Japanese Okonomiyaki-Style Egg Sandwich with Bonito Flakes and Mayo
A warm, indulgent breakfast sandwich inspired by okonomiyaki flavors. Fluffy shokupan (Japanese milk bread) cradles a perfectly fried egg and is layered with tangy okonomiyaki sauce, creamy Japanese mayo, and topped with delicate bonito flakes that dance from the heat. This is comfort food that bridges the gap between a traditional breakfast and a savory pancake in sandwich form.
Steps
Before you start
- Have all ingredients measured and ready near your cooking station
- Use fresh eggs at room temperature for even cooking
- Keep bonito flakes sealed until the last moment so they stay crisp
Mix mayo and sauce
- In a small bowl, combine 2 tablespoons (30 g) Japanese mayo with 3 tablespoons (45 ml) okonomiyaki sauce, stirring until smooth.
- Set aside.
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Ready when: Mixture is smooth and evenly blended
Tip: Mix these two ahead of time so you can work quickly once the eggs hit the pan
Heat butter and cook eggs
- Heat a 10-inch (25 cm) nonstick skillet over medium-high heat (about 6 out of 10).
- Add 1 tablespoon (14 g) butter and let it melt and foam, about 30 seconds.
- Crack both eggs into the center of the pan and season immediately with a pinch of kosher salt and black pepper.
- Cook for 3–4 minutes until the whites are set but the yolks still jiggle slightly when you tilt the pan.
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Ready when: Egg whites are opaque and set; yolk jiggles softly when pan is tilted
Tip: Don't let the pan get too hot or the bottoms will brown before the whites set. Watch the eggs constantly
Toast bread lightly
- While the eggs cook, place 4 slices of shokupan on a separate skillet or griddle over medium heat (about 4 out of 10), or use a toaster.
- Toast for 1–2 minutes per side until pale golden and warm throughout but not dry.
- Transfer to a clean surface.
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Ready when: Bread is warm and lightly golden, still soft inside
Tip: Light toasting gives structure for the wet fillings without making the bread hard or brittle
Assemble sandwiches
- Arrange 2 slices of toasted bread on a clean work surface.
- Spread half of the mayo-sauce mixture (about 2 tablespoons/30 g) on the inside of each slice.
- Carefully slide the cooked eggs onto one slice of bread from each sandwich.
- Drizzle the remaining 1 tablespoon (15 ml) okonomiyaki sauce over the eggs, then top each with the second slice of bread.
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Ready when: Both sandwiches are stacked and ready to top
Tip: Work quickly while the eggs are warm; the warmth will slightly soften the mayo and sauce, creating a creamy texture
Add bonito flakes and serve
- Gently open the top of each sandwich and scatter about ½ ounce (7 g) bonito flakes over the warm egg.
- The heat will make the thin flakes wave and dance.
- Close the sandwich and serve immediately, while the bread is still warm and the egg yolk is warm and runny.
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Ready when: Bonito flakes are placed and sandwich is closed
Tip: Bonito flakes are delicate and will become soggy if left too long; add them as the final step before eating
Good to know
Tips
- Okonomiyaki sauce is available at most Asian grocery stores and online. Storing it in the pantry extends its life indefinitely; there's no need to refrigerate after opening
- The key to this sandwich is contrast: warm bread, runny egg yolk, creamy mayo, tangy sauce, and the delicate floral nuttiness of bonito flakes. Don't skip any component
- For a striped presentation (very authentic), drizzle the mayo in thin crisscross lines rather than spreading it evenly
- If your eggs are larger than large, you may need a third slice of bread per sandwich to contain the yolk without it running out the sides
Storage & reheating
Best eaten fresh and warm. Leftover sandwiches can be wrapped in foil and refrigerated for up to 1 day, but the bread will soften. Reheat in a 350°F (175°C) oven for 3–4 minutes to warm through and restore some crispness to the bread.
Substitutions
- shokupan (Japanese milk bread) or brioche → brioche, soft white sandwich bread, or challah. Use thick slices (about ½-inch/1.25 cm) to provide structure. Avoid dense whole-grain breads, which will feel heavy with the fillings
- Japanese mayonnaise (Kewpie) → regular mayonnaise mixed with a pinch of monosodium glutamate (MSG) or a touch of fish sauce. Japanese mayo has a richer, slightly sweet taste. Regular mayo with a savory boost is a reasonable substitute, though the flavor will be slightly less umami-rich
- okonomiyaki sauce → half Worcestershire sauce and half ketchup, with a pinch of soy sauce. This approximates the sweet, tangy, savory flavor of okonomiyaki sauce. Use equal parts by volume
- bonito flakes (katsuobushi) → aonori (green seaweed powder) or toasted nori strips. These add umami and visual interest but lack the dancing texture. Bonito flakes are worth seeking out for the full okonomiyaki experience
