Preheat your oven to 350°F (175°C). Line a 9x13 inch baking pan with parchment paper, leaving an overhang on the sides for easy lifting. Lightly grease the parchment.

In a large bowl, whisk together the flour, baking powder, salt, and ½ cup granulated sugar.

In a separate medium bowl, whisk together the eggs, milk, vegetable oil, and 1 tsp vanilla extract until well combined.

Pour the wet ingredients into the dry ingredients and mix with a rubber spatula until just combined and smooth. Be careful not to overmix.

Pour the batter evenly into the prepared baking pan. Bake for 12-15 minutes, or until a toothpick inserted into the center comes out clean and the cake is lightly golden.

Let the cake cool in the pan for 10 minutes, then use the parchment paper overhang to lift it onto a wire rack to cool completely.

While the cake cools, place the thinly sliced strawberries in a small bowl. Sprinkle with 2 tbsp granulated sugar and gently toss to combine.

Let the strawberries sit at room temperature for at least 15 minutes, stirring occasionally, until they release some of their juices.

In a large, chilled bowl (or the bowl of a stand mixer), combine the very cold heavy cream, powdered sugar, and ½ tsp vanilla extract. Using an electric mixer with the whisk attachment, beat on medium-high speed until stiff peaks form. Be careful not to overbeat, or it will turn to butter.

Cover and refrigerate until ready to use.

Line a baking sheet with parchment paper.

Melt the dark chocolate: You can do this in a microwave-safe bowl in 30-second intervals, stirring after each, until smooth, or in a double boiler over simmering water.

Pour the melted chocolate onto the parchment-lined baking sheet and spread it very thinly and evenly using an offset spatula or the back of a spoon. Aim for a layer about 1mm thick.

Place the baking sheet in the refrigerator for 5-10 minutes, or until the chocolate is firm but still pliable.

Once firm, use a sharp knife or pizza cutter to cut the chocolate into thin strips, approximately ¼ inch wide and 2-3 inches long, to act as 'nori' bands. Carefully peel them off the parchment. Keep refrigerated until assembly.

Once the cake is completely cool, use a sharp knife to trim the edges and then cut the cake into approximately 1x2 inch rectangles (you should get about 24 pieces).

Arrange the cake rectangles on a serving platter.

Pipe or spoon a dollop of whipped cream onto the top of each cake rectangle.

Place a few slices of macerated strawberry on top of the whipped cream.

If using, gently wrap a chocolate 'nori' strip around the middle of each "sushi" piece, pressing lightly to secure.

Serve immediately or refrigerate until ready to serve.