1. Preheat oven to 450°. Flatten four paper baking cups and place in a shallow baking pan. Center one single-serving dessert sponge cake (the type sold for making individual strawberry shortcakes) on each paper circle. Place a generous scoop of strawberry ice cream on each cake. Freeze at least 30 minutes; wrap airtight if freezing longer than a few hours.
2. In a large bowl, with an electric mixer on high speed, beat 4 egg whites with 1/2 teaspoon cream of tartar until foamy. Gradually beat in 1/2 cup sugar, a tablespoon at a time, until stiff, glossy peaks form. Spread meringue evenly over each cake and ice cream, sealing meringue to paper. Sprinkle evenly with about 1 tablespoon chopped toasted nuts or shredded coconut, if desired.
3. Bake until lightly browned, 2 to 3 minutes. Transfer to plates and serve immediately with sweetened sliced fruit or your favorite ice cream topping.