Instant Pot Spinach and Ricotta-Stuffed Pasta Shells

Name: Instant Pot Spinach and Ricotta-Stuffed Pasta Shells
Prep time: 20 min
Cook time: 12 min
Total time: 32 min
Yield: 4 servings
Cuisine: Italian
Ingredients: 12 shells jumbo pasta shells (about 1 pound box), cooked al dente, drained and cooled slightly; 10 oz (280 g) frozen spinach, thawed and squeezed completely dry; 15 oz (425 g) whole-milk ricotta, room temperature; 1 cup (113 g) shredded whole-milk mozzarella, divided; ½ cup (50 g) grated Parmigiano-Reggiano; 1 large egg, room temperature; 2 garlic cloves, minced; kosher salt; freshly ground black pepper; ¼ tsp (½ g) ground nutmeg; 24 oz (680 g) marinara sauce or crushed tomatoes; 1 cup (237 ml) water; 1 tsp dried Italian seasoning (optional)

From the MyKitchenBank Kitchen

Tender jumbo pasta shells filled with a creamy ricotta and spinach mixture, cooked directly in a rich tomato sauce using an Instant Pot. This one-pot vegetarian dish comes together quickly with minimal cleanup—perfect for weeknight dinners or feeding a crowd. The shells stay intact and the filling stays moist, all finished in under 30 minutes.

Prep: 20 min
Cook: 12 min
Wait: 5 min
Total: 37 min
Makes: 12–14 stuffed shells (serves 4)

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Steps

Before you start

Thaw frozen spinach and squeeze completely dry to prevent a watery filling
Spread a thin layer of sauce on the bottom of the Instant Pot to prevent the shells from sticking
Have all filling ingredients measured and ready before assembling shells
Read the Instant Pot manual if unfamiliar with quick-release pressure venting

1
Cook the pasta shells
- Bring a large pot of salted water to a boil.
- Add jumbo pasta shells and cook for 2 minutes less than the package directions to keep them firm for stuffing.
- Drain in a colander and lay on a clean kitchen towel to cool slightly (about 5 minutes).
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Ready when: Shells are tender but still hold their shape and are not falling apart
Tip: Undercooking by 2 minutes ensures the shells don't split open when stuffed and won't turn mushy after pressure cooking.
2
Mix the ricotta filling
- In a large bowl, combine thawed and squeezed-dry spinach, ricotta, 0.75 cup of shredded mozzarella, Parmigiano-Reggiano, egg, minced garlic, 0.5 tsp salt, a pinch of black pepper, and ground nutmeg.
- Stir until well combined and the mixture is smooth with no lumps.
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Ready when: Mixture is creamy and evenly blended with no visible dry spinach
Tip: Squeeze the spinach very thoroughly; excess moisture will make the filling leak and the sauce thin. Use a clean kitchen towel and press hard.
3
Fill the shells
- Using a spoon or small ice cream scoop, fill each cooled shell with about 1.5 tablespoons of ricotta filling, packing it gently but firmly.
- Arrange filled shells open-side up on a clean surface.
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Ready when: All shells are uniformly filled and stable
Tip: If you overfill, the ricotta will burst out during cooking. Pack the filling snugly into the cavity but don't exceed the rim of the shell.
4
Prepare the Instant Pot
- Spread 0.5 cup of marinara sauce or crushed tomatoes evenly across the bottom of the Instant Pot to create a thin base layer.
- This prevents the shells from sticking to the pot bottom.
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Ready when: Bottom of pot is coated with a thin, even layer of sauce
Tip: Do not skip this step or the shells will stick and break. A thin layer is enough—you don't need much.
5
Layer the filled shells
- Carefully arrange stuffed shells in the Instant Pot in a single layer, open-side up, in a circle or spiral pattern.
- If you have more shells, create a second gentle layer on top.
- Pour the remaining 1.5 cups of marinara sauce mixed with 1 cup of water evenly over and around the shells.
- Do not stir; keep shells upright.
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Ready when: Shells are arranged stably and sauce coats them gently
Tip: Keep the shells open-side up so the filling doesn't tumble out. Gentle layering is key; don't jostle the pot or press down on the shells.
6
Pressure cook the shells
- Lock the lid onto the Instant Pot and set the valve to Sealing.
- Cook on high pressure for 4 minutes.
- This cooks the shells through while keeping the filling creamy and the sauce flavorful.
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Ready when: Instant Pot beeps when pressure cooking is complete
Tip: Do not use manual release immediately; allow natural pressure release for 2 minutes to prevent the shells from breaking apart from sudden pressure loss.
7
Release pressure and open the pot
- When the Instant Pot beeps, let the pressure release naturally for 2 minutes.
- Turn the valve to Venting to release any remaining pressure.
- Wait 30 seconds, then carefully remove the lid, opening it away from your face to avoid the steam.
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Ready when: Steam is fully vented and the lid opens easily without resistance
Tip: A slow pressure release is crucial; rushing this step risks shells falling apart or the ricotta mixture rupturing out of the filling.
8
Finish with melted cheese
- Sprinkle the remaining 0.25 cup of mozzarella over the hot shells.
- Cover the pot (without locking) for 1–2 minutes until the cheese melts.
- If desired, stir in Italian seasoning to the sauce.
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Ready when: Mozzarella is fully melted and creamy
Tip: Add the extra cheese after cooking, not before; it prevents browning and ensures a fresh, creamy finish.
9
Rest and serve
- Let the stuffed shells rest in the pot for 3–5 minutes.
- Using a wide, shallow spoon, carefully transfer shells to serving plates or a shallow bowl, spooning sauce over top.
- Serve hot.
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Ready when: Shells are stable and sauce has thickened slightly
Tip: Let the shells cool slightly in the hot sauce so they firm up enough to transfer without falling apart or spilling filling.

Good to know

Tips

Squeeze the thawed spinach very thoroughly over a clean kitchen towel, wringing out as much moisture as possible. Watery spinach is the #1 cause of a loose, runny filling and thin sauce.
Cook the pasta shells just under al dente so they hold their shape in the pressure cooker. Overcooked shells will split and lose their filling.
Do not stir the pot during or after pressure cooking. Keep the shells upright and undisturbed so they don't break apart or release too much filling into the sauce.
For a prettier presentation, reserve a small handful of fresh basil or a sprinkle of parsley; add it just before serving for color and fresh herbal notes.

Make ahead

Stuff the shells up to 4 hours ahead; cover with plastic wrap and refrigerate. If cooking from cold, add 2–3 minutes to the pressure-cooking time.

Storage & reheating

Refrigerate leftovers in an airtight container for up to 3 days. Reheat gently in a microwave (covered, 2–3 minutes per serving) or on the stovetop over low heat in a covered skillet with a splash of water. Freeze for up to 2 months; thaw overnight in the fridge before reheating.

Substitutions

frozen spinach → 10 oz fresh spinach, wilted and squeezed dry. Fresh spinach yields the same result as frozen; cook it down over medium heat for 3–4 minutes, then squeeze very dry.
whole-milk ricotta → 15 oz drained plain Greek yogurt or labneh. Creates a tangier filling with a slightly firmer texture. Mix well to avoid curdling during cooking.
shredded whole-milk mozzarella → shredded provolone or a mix of fontina and mozzarella. Provolone adds a more robust, savory flavor; fontina brings a nuttier profile.
marinara sauce or crushed tomatoes → 30 oz canned diced or whole tomatoes plus 1 tbsp tomato paste and 1 tsp garlic powder. Gives a chunkier, more rustic sauce; stir in the tomato paste to concentrate the flavor and prevent excess liquid.