Preheat oven to 350°F (175°C). Grease and flour two 8-inch round cake pans (or three 6-inch pans) and line bottoms with parchment.

Whisk together 2 ¼ cups flour, 2 ¼ tsp baking powder, and 1 tsp salt in a bowl. Set aside.

In a large bowl, cream ¾ cup softened butter with 1 ½ cups granulated sugar until pale and fluffy, about 3–5 minutes using a mixer.

Beat in 5 large egg whites one at a time until combined, then stir in 2 tsp vanilla.

With mixer on low, add the dry mix in three additions, alternating with the 1 cup pink champagne, starting and ending with dry ingredients. Mix just until combined; do not overmix. Add pink gel coloring if desired.

Divide batter evenly between prepared pans. Bake 25–30 minutes for 8-inch pans, or until a toothpick comes out clean.

Let cakes cool in pans for 10–15 minutes, then turn out onto a wire rack to cool completely.

Beat 1 ½ cups softened butter until creamy. Gradually add 6 cups powdered sugar, then slowly pour in 2/3 cup pink champagne and 1 tsp vanilla.

Add a pinch of salt to balance if needed and tint with gel coloring. Adjust consistency with more powdered sugar or milk/champagne as necessary.

Level cake layers if needed. Place first layer on a cake board, spread a thin layer of frosting, stack next layer, then crumb-coat the whole cake and chill for 20–30 minutes.

Finish with a smooth outer coat of frosting, then melt white chocolate for a drip with cream and let cool slightly.

Create a drip around the top edge and top with chocolate-dipped strawberries and champagne marshmallows as desired. Chill briefly to set the drip.