Preheat oven to 350°F (175°C). Line several 8-inch round cake pans with parchment paper and spray lightly with non-stick spray.

In a massive bowl, whisk together melted butter, brown sugar, and granulated sugar until smooth. Add eggs, yolks, and vanilla extract, whisking well.

Gently fold in the flour, baking soda, and salt until just combined. Fold in the chocolate chips.

Divide dough evenly among prepared pans (about 1 to 1.5 cups per pan). Press into an even layer.

Bake for 12-15 minutes until edges are golden. Let cool in pans for 15 minutes before transferring to wire racks to cool completely.

For the frosting: Beat softened butter for 5 minutes until pale and fluffy. Gradually add powdered sugar, then vanilla, heavy cream, and a pinch of salt. Whip until thick and airy.

To assemble: Place one cooled cookie on a cake stand. Pipe a thick, even layer of buttercream on top. Top with another cookie. Repeat until all layers are stacked.

Decorate the top and base with food-safe fresh flowers if desired. Chill the cake for 2 hours to set the frosting before slicing.