Preheat your oven to 350°F (175°C) and prepare a 10x15 inch jellyroll pan by greasing and lightly dusting with flour.
In a large bowl, beat the eggs and egg yolks using an electric mixer.
Gradually add sugar and continue beating until the mixture becomes thick and pale, about 10 minutes.
If you're using a stand mixer, the whisk attachment works best.
Sift the flour and baking powder into the egg mixture and fold by hand, along with the milk.
Stir gently until just combined, then fold in the melted butter until smooth.
Evenly spread the batter into the prepared pan.
Bake for 12 to 15 minutes or until a toothpick inserted into the center comes out clean.
Once baked, carefully invert the cake onto wax paper and allow it to cool completely.
This ensures evenly shaped petits fours.
After cooling, cut the cake into small squares, triangles, or rectangles.
Place the pieces on a wire rack or glazing screen with space between them.
Set the rack over wax paper to catch any drips.
Warm the petit four icing and pour or spoon it over the small cakes.
Scrape up any drippings to reheat and reuse.
Let the icing set completely.
Once dry, carefully lift the cakes with a metal spatula and trim the bottoms if needed.
Place each petit four in a small muffin paper for easy serving.
Decorate as desired.