In the bowl of a stand mixer fitted with the whisk, combine eggs and sugar. Mix on high for 8-10 minutes or until the mixture is pale and falls in a ribbon-like consistency. Add vanilla and mix for 15 seconds.
In a separate large bowl, sift together flour, matcha, baking powder, and salt. Gently fold the flour mixture into the egg mixture until combined. Pour in the butter and mix by hand with a spatula until thick and glossy.
Transfer the batter to a bowl and cover it airtight. Refrigerate overnight, or for at least 2 hours.
After it has rested, preheat the oven to 400°F (200°C). Prepare the pans by brushing with melted butter. If you don’t have a 15-well pan or 2 pans, just bake in batches.
Using a scoop, spoon 1½ tablespoons of batter into each mold. With a greased finger, gently press the edges of the batter into the mold. The batter should be thick, resembling cookie dough.
Bake for 4 minutes, then lower to 330°F (165°C) and bake for 8-10 minutes until domed in the center and edges are set. This temperature change gives them their signature bump.
Cool on a wire rack. Meanwhile, melt the white chocolate wafers according to the package. Then mix in matcha powder and separately some strawberry powder, if using.
Pour 1 teaspoon of melted strawberry (or matcha) coating into each mold and press the cake in place. Repeat for all, then refrigerate for 1 hour or until the chocolate has set.
Enjoy!