Combine the sauce ingredients (3 tbsp Worcestershire sauce, 1 tbsp tomato ketchup, 1 tsp Japanese soy sauce (koikuchi shoyu), 1 tsp mirin, 1 tsp honey and ⅛ tsp dashi granules) in a saucepan and bring to a gentle simmer over medium heat. Mix continuously to prevent splattering. Use a spatula to scrape the bottom of the pan and prevent burning.
Simmer the sauce for 3 minutes or until slightly thickened, then remove from the heat and set aside for later.
Next, take a mixing bowl, pour in 500 ml dashi stock and 1 tsp Japanese light soy sauce (usukuchi shoyu). Crack 1 egg into the bowl and whisk until combined.
Measure out 100 g cake flour in a separate bowl and make a well in the center. Pour the dashi mixture into the well while whisking until it forms a smooth batter.
Cut 120 g boiled octopus into small pieces (approx 1 inch / 2.5cm) and finely chop 4 tbsp red pickled ginger (benishoga) and 50 g finely chopped green onions.
Heat up the takoyaki pan and generously coat the mold with toasted sesame oil. Brush the oil into each crevice until evenly coated. (If you don't have a brush, spread the oil using kitchen paper.)
Once the takoyaki pan is hot (almost smoking), pour the batter into the mold, filling the crevices half way.
Place a piece of octopus in each slot and then fill the entire mold with batter, including the areas around each slot.
Sprinkle the chopped green onion, chopped pickled ginger and 30 g tempura flakes (tenkasu) generously over the top of the wet batter and allow to cook for 1-2 minutes.
Using a long bamboo skewer (or similar), draw horizontal and vertical lines between all the slots to divide the batter around each takoyaki.
Roll each takoyaki about half way by scraping the bamboo skewer around the edge of the slot in a circular motion with your wrist. It's okay if the shape is still messy at this point. Leave to cook for a few minutes.
Roll the takoyaki again, tucking any messy parts into the bottom to shape it nicely. After the second roll it should already be more or less round.
Once the takoyaki is round enough, brush with another layer of sesame oil and keep rolling the takoyaki one by one.
Swap any pale takoyaki with the more golden ones to ensure even cooking. (This is due to the inevitable heat spots on the pan, generally the ones in the middle directly over the heat source cook faster.)
Once the outside looks golden and crisp, remove the takoyaki from the pan. (The middle is still usually a bit runny, this is normal and you don't need to cook it until it's firm all the way through.)
Place the cooked takoyaki on a plate and brush the with the sauce from earlier. Drizzle with mayonnaise and sprinkle with your choice of toppings. Repeat until all the batter and ingredients are used up, enjoy!
Notes
Octopus alternatives: Shrimp, squid, scallops, sausage, cheese, beef, king oyster mushrooms.Fridge: Airtight container, up to 24 hours. Store plain without any sauces or toppings.Freezer: Tray-freeze plain balls, then transfer to an airtight bag, press out air. Up to 1 month.Meal Prep: Batter can be prepared 24 hours ahead and refrigerated. Pre-cut octopus, pickled ginger, and green onions can be stored separately in airtight containers for same-day use.Reheating: Microwave 30-60 seconds uncovered (to release steam), then immediately transfer to preheated toaster oven for 3-5 minutes until exterior crisps. For frozen: microwave 3-5 minutes to defrost, then toaster oven.