Slow Cooker Sourdough Lentil and Harissa Soup with Crispy Bread

Name: Slow Cooker Sourdough Lentil and Harissa Soup with Crispy Bread
Prep time: 15 min
Cook time: 3 h
Total time: 3 h 15 min
Yield: 4 servings
Cuisine: Moroccan
Ingredients: 1½ cups (280 g) red lentils, rinsed; 3 cups (150 g) sourdough bread, cut into ½-inch cubes, divided (2 cups for soup, 1 cup for crisping); 3 tablespoons (50 g) harissa paste; 1 can (800 ml) canned crushed tomatoes (28 oz); 4 cups (950 ml) vegetable or chicken broth; 1 large (200 g) yellow onion, diced; 4 cloves (20 g) garlic, minced; 1½ teaspoons (3 g) ground cumin; 1 teaspoon (2 g) sweet paprika; ¾ teaspoon (5 g) kosher salt; ¼ teaspoon (½ g) black pepper, freshly ground; 2 tablespoons (30 ml) olive oil; 2 tablespoons (30 ml) extra virgin olive oil; 1 whole (50 g) lime, cut into wedges for serving; ½ cup (15 g) fresh cilantro, roughly chopped; ½ teaspoon (1½ g) cumin seeds (optional)

From the MyKitchenBank Kitchen

A warming North African-inspired soup built on a foundation of red lentils, harissa paste, and tomatoes, slow-cooked until deeply flavored and velvety. Sourdough cubes are both simmered in the broth to add body and toasted until crispy to serve as a textured garnish. Finished with cilantro, lime, and a drizzle of olive oil for brightness and richness.

Prep: 15 min
Cook: 3 hr
Total: 3 hr 15 min
Makes: 4 servings (about 6 cups soup plus crispy bread)

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Ingredients

4 servings

1½ cups (280 g) red lentils, rinsed
3 cups (150 g) sourdough bread, cut into ½-inch cubes, divided (2 cups for soup, 1 cup for crisping)
3 tablespoons (50 g) harissa paste
1 can (800 ml) canned crushed tomatoes (28 oz)
4 cups (950 ml) vegetable or chicken broth
1 large (200 g) yellow onion, diced
4 cloves (20 g) garlic, minced
1½ teaspoons (3 g) ground cumin
1 teaspoon (2 g) sweet paprika
¾ teaspoon (5 g) kosher salt
¼ teaspoon (0.5 g) black pepper, freshly ground
2 tablespoons (30 ml) olive oil
2 tablespoons (30 ml) extra virgin olive oil
1 whole (50 g) lime, cut into wedges for serving
½ cup (15 g) fresh cilantro, roughly chopped
½ teaspoon (1.5 g) cumin seeds (optional)

Equipment (7)

6-quart slow cooker
Cutting board
Chef's knife
Large wooden spoon
Measuring cups and spoons
Small skillet (8-inch)
Tongs or slotted spoon

Steps

Before you start

Slice sourdough into ½-inch cubes about 2 hours before serving to allow them to firm up slightly for crisping
Have your slow cooker on hand and ready to use
Taste harissa paste beforehand—heat levels vary; start with the amount given and adjust in the final step
Gather cilantro and lime for finishing

1
Prepare and add base
- In your 6-quart slow cooker, combine the rinsed red lentils, canned crushed tomatoes with their liquid (about 28 oz / 800 ml), vegetable broth (4 cups / 950 ml), diced yellow onion (about 1 large onion, 200 g), and minced garlic (4 cloves, 20 g).
- Stir in the ground cumin (1.5 tsp), sweet paprika (1 tsp), kosher salt (¾ tsp), and black pepper (¼ tsp).
- Gently fold in 2 cups (100 g) of the sourdough bread cubes—these will partially break down and thicken the soup while it cooks.
- Add the harissa paste (3 tablespoons / 50 g) and stir until combined, breaking up any lumps.
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Tip: Stir the harissa paste well to distribute its spice evenly; don't let it clump at the bottom.
2
Cook on low in slow cooker
- Cover the slow cooker and cook on low for 3 hours (180 minutes).
- The lentils should completely break down, the soup will thicken considerably, and the flavors will meld.
- Do not stir during cooking—the undisturbed environment helps the soup develop its full flavor.
- At the 2.5-hour mark, you can briefly check that the liquid hasn't reduced too much; if it looks very thick, you've caught it at the right time.
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Ready when: Lentils have completely disintegrated, the soup is creamy and cohesive, and the color is a rich, deep rust-orange
Tip: Do not lift the lid frequently or stir; each opening releases heat and lengthens cooking time.
3
Crisp the sourdough cubes
- While the soup finishes its final 30 minutes, heat 2 tablespoons (30 ml) of olive oil in a small 8-inch skillet over medium-high heat.
- Once the oil shimmers, add the remaining 1 cup (50 g) of sourdough bread cubes and toss frequently with tongs or a wooden spoon for 6–8 minutes, until the cubes are deep golden brown and crunchy on all sides.
- Watch closely—they can brown quickly.
- Transfer to a paper towel to drain and cool slightly.
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Ready when: Bread cubes are deep golden brown and crispy throughout; no soft centers remain when you break one open
Tip: Toss constantly to prevent burning and ensure even crisping. Work in the final 30 minutes of slow cooking to serve them warm.
4
Season and taste
- Once the slow cooker time is complete, carefully taste the soup.
- The harissa provides heat and depth; if you prefer more spice, stir in an additional ½–1 tablespoon of harissa paste.
- Taste for salt and pepper, adjusting as needed.
- The soup should be velvety and rich, with a pleasant spice that builds gradually rather than overwhelming.
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Tip: Taste conservatively when adding more harissa; you can always add more, but you cannot remove it.
5
Finish with oil and herbs
- Drizzle 2 tablespoons (30 ml) of extra virgin olive oil across the surface of the soup and stir gently to incorporate.
- Add the roughly chopped fresh cilantro (about ½ cup / 15 g).
- If using, scatter the optional cumin seeds (½ tsp) over the surface for added fragrance and a toasty note.
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Tip: Add the cilantro just before serving so it remains bright and aromatic rather than wilting into the soup.
6
Serve
- Ladle the soup into bowls.
- Top each serving with a generous handful of the crispy sourdough cubes.
- Serve with lime wedges on the side so each diner can squeeze fresh juice to taste, balancing the richness and spice of the soup.
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Tip: Add crispy bread cubes right before serving; if added too early, they'll begin to soften from the heat and moisture of the soup.

Good to know

Tips

Dice your onion and mince your garlic before you begin; this is a minimal-prep recipe that benefits from everything being ready to go.
The quality of your harissa paste matters significantly. Some brands are smokier, some spicier; taste a small bit beforehand so you can adjust confidently.
For extra creaminess without cream, use an immersion blender to partially blend the finished soup, leaving it rustic rather than completely smooth.
Sourdough bread used in slow cooking loses its structural integrity as its starches absorb liquid. Using a day-old loaf (not fresh) and letting the cubes sit out slightly before cooking helps them hold together a bit longer.

Make ahead

The soup can be made up to 2 days ahead (without the crispy bread cubes). Cool to room temperature, refrigerate in an airtight container, and reheat gently on low in the slow cooker or on the stovetop over medium-low heat, stirring occasionally, until warmed through (about 20–30 minutes on the stovetop). Crisp the sourdough cubes fresh just before serving.

Storage & reheating

Store the finished soup in the refrigerator in an airtight container for up to 3 days. The crispy bread cubes are best served the day they are made but can be stored in an airtight container at room temperature for up to 1 day (they will gradually soften). Freeze the soup (without crispy bread) in freezer-safe containers or bags for up to 2 months. Thaw overnight in the refrigerator and reheat gently over medium-low heat on the stovetop or in the slow cooker, then crisp fresh bread cubes before serving.

Substitutions

harissa paste → 2 tablespoons of sriracha or chili paste mixed with ½ tablespoon tomato paste. This will give heat and depth, though with slightly different flavor. Start with less and taste as you go.
red lentils → 1.5 cups (280 g) brown or green lentils. Brown and green lentils will hold their shape longer and won't fully break down; add them 15 minutes later in the cooking process so the soup isn't overly thick, and expect a chunkier texture.
sourdough bread → 3 cups (150 g) crusty bread or focaccia, cubed. Any sturdy bread will work; sourdough's tang is nice but not essential. Avoid soft sandwich bread, which will turn to mush.
fresh cilantro → 2 tablespoons fresh mint or parsley, chopped. Mint adds a cool note; parsley is milder. Both work well but shift the flavor profile slightly.