Preheat the oven to 350F. Line a 8x8-inch baking pan with parchment paper. Grease the bottom and sides of the pan with nonstick cooking spray. Set aside.
Combine the gluten-free flour blend, baking soda, and salt together.
Add the cocoa powder and hot melted butter together. Stir until the mixture forms a smooth paste. Let sit for 2-3 minutes to let the cocoa powder bloom.
Add the granulated sugar and brown sugar to the chocolate mixture. Mix for 1 minute, until smooth.
Add the eggs and vanilla to the wet ingredients. Mix for an additional minute, until well combined.
Gradually add the dry ingredients to the wet ingredients. Mix until no more streaks of flour remain. Do not over mix the batter.
Pour the brownie batter into the prepared baking pan. Spread with a spatula into an even layer, making sure to reach the corners.
Roughly chop 1 cup of the mini eggs, leaving the lest whole for later. Add the roughly chopped mini eggs to the top of the brownie batter.
Bake at 350F for 22-25 minutes, rotating the pan halfway through. Bake until the edges of the brownies are set. A toothpick inserted into the center will come out mostly clean with some wet crumbs. Do not overbake the brownies.
Immediately top with the remaining whole mini eggs.
Let the pan sit on a wire rack until cool. Use the parchment paper overhang to remove the brownies from the pan to a cutting board. Cut into squares.