In a large bowl, combine 1 cup (120 g) all-purpose flour, ¼ tsp. salt, ¼ tsp. sugar, and ¼ tsp. baking powder and mix all together.
Peel and grate nagaimo in a small bowl.
Add the grated nagaimo and dashi in the bowl.
Mix all together till combined. Cover the bowl with plastic wrap and let it rest in the refrigerator for at least one hour.
Make Okonomiyaki Sauce
Gather all the ingredients for Okonomiyaki Sauce.
To make homemade Okonomiyaki Sauce, combine 1 ½ Tbsp. sugar, 2 Tbsp. oyster sauce, 4 Tbsp. ketchup, and 3 ½ Tbsp. Worcestershire sauce in a small bowl. Mix all together until sugar is completely dissolved.
Remove the core of the cabbage and mince it. Set aside to let the moisture evaporate so it won’t dilute the batter.
Cut the pork belly slices in half and set aside.
Take out the batter from the refrigerator and add 4 large eggs, ½ cup (8 Tbsp.) tempura scraps (Tenkasu/Agedama), and ¼ cup (4 Tbsp.) pickled red ginger (Kizami Beni Shoga) in the bowl. Mix well until well-combined.
Add chopped cabbage to the batter 1/3 at a time. Mix well before adding the rest.
In a large pan, heat vegetable oil on medium heat. When the frying pan is hot (400F/200C), spread the batter in a circle on the pan. We like thicker okonomiyaki (final thickness is ¾ inches (2 cm)). If you’re new to making okonomiyaki, make a smaller and thinner size so it’s easier to flip.
Place 2-3 sliced pork belly on top of Okonomiyaki and cook covered for 5 minutes.
When the bottom side is nicely browned, flip over.
Gently press the okonomiyaki to fix the shape and keep it together. Cover and cook for another 5 minutes.
Flip over one last time and cook uncovered for 2 minutes. If you’re going to cook next batch, transfer to a plate.
Serving & Preserving
Here are the ingredients for toppings. Apply okonomiyaki sauce with brush, add Japanese mayonnaise in zigzagging lines (optional), and sprinkle dried bonito flakes (katsuobushi). You can also put dried green seaweed (aonori), chopped green onions, and pickled red ginger on top for garnish. Please see the video for this step.
If you have a Japanese griddle with a lid (We call it “Hot Plate”), you can cook several okonomiyaki at once! Otherwise, I recommend cooking two okonomiyaki (each in one frying pan) at a time.
Okonomiyaki freezes well. Once it cools down (no sauce or toppings), wrap each okonomiyaki in aluminum foil and put it in a freezer bag. When you want to eat it, defrost first and put it in a toaster oven or oven to heat it up. It's a great quick meal!
Dashi: If you don't have homemade dashi, you can use 3/4 cup water + 1 tsp. granulated dashi (dashi powder).
Sliced Pork Belly: You can use shrimp, squid, or other ingredients instead.