Preheat the oven to 350°F.
Line a 9x13-inch baking pan with parchment paper.
Lightly grease the parchment and exposed pan sides.
In a large bowl, whisk the melted butter, granulated sugar, and brown sugar.
Add the eggs and 1 tablespoon vanilla extract.
Whisk until glossy and well combined.
Stir in the cocoa powder, flour, salt, and baking powder.
Mix just until no dry streaks remain.
Fold in the chocolate chips.
Spread the batter evenly into the prepared pan.
Bake for 28 to 34 minutes.
Check for moist crumbs in the center.
Cool completely in the pan.
Lift the brownies out using the parchment.
Chill for 20 to 30 minutes for cleaner cutting.
Cut the brownies into egg shapes using a paper template and a knife or an egg-shaped cookie cutter.
Beat the cream cheese and 4 tablespoons softened butter until smooth.
Add the powdered sugar and 1 teaspoon vanilla extract.
Mix until fluffy.
Add the heavy cream or milk, one spoonful at a time, if needed.
Tint part or all of the frosting pale yellow with a few drops of yellow food coloring.
Pipe or spoon the topping onto the center of each egg-shaped brownie.
Add Easter sprinkles, if using.
Chill briefly before serving if your kitchen runs warm.