For the cupcakes: Preheat the oven to 325 degrees F. Line a cupcake or muffin pan with 12 regular-size cupcake liners.

Sift the flour, baking powder, wheat germ, ground ginger, and salt into a medium-size bowl. Set the bowl aside. In the bowl of an electric stand mixer, with a paddle attachment, cream the butter and sugar together, about 6 minutes. Scrape down the sides of the bowl then add the vanilla and 1 egg yolk at a time, scraping down the sides of the bowl after each addition. Turn the mixer to low speed, and add the flour mixture in a steady stream. Turn the mixer to medium speed and beat for 2 minutes. Slowly add the cream. In a separate, grease-free bowl, whisk the egg whites with an electric hand beater and a pinch of salt until they form stiff but moist peaks. Gently stir into the batter by hand with a spatula until no whites are visible.

Fill the cupcake liners half full with batter and bake until they are golden and spring back when touched, about 30 minutes. Cool the cupcakes in their pan for 5 minutes before transferring to a cooling rack.

For the wasabi cream filling: Whip the cream cheese and wasabi paste by hand with a metal spoon in a small bowl. Cover until ready to use.

For the tuna creme fraiche topping: Combine the creme fraiche with 2 1/2 tablespoons of the sesame seeds and 3/4 teaspoon ginger, mixing by hand with a spoon in a medium-size bowl. Pass the tuna through a hand-held zester to form small ribbons. Add the tuna to the creme fraiche and continue mixing. Add the lemon juice and mix until an even consistency is reached.

To assemble: Remove and discard the center of each cooled cupcake using an apple corer. Pipe the wasabi filling into each cavity until level with the top of the cake. Generously dollop the tuna creme fraiche mixture on top and sprinkle with remaining sesame seed and ginger mixture. Decorate with 1 wasabi pea placed in the center of the cake