Preheat the oven to 325F (180C). Line a 8x8-inch square baking pan with parchment paper. Set aside.

In a medium mixing bowl, add the gluten-free flour blend, cornstarch, baking powder, and salt. Whisk to combine. Set aside.

In a large mixing bowl, add the melted butter and brown sugar. Mix until combined.

Add the egg, egg yolk, and vanilla extract. Mix until smooth.

Add in the dry ingredients, mixing until no more streaks of gluten-free flour remain.

Roughly chop ¾ cup of the mini chocolate eggs into small pieces. Reserve the remaining ¼ cup of mini chocolate eggs whole for later.

Add the roughly chopped mini eggs to the batter and stir until combined.

Pour the blondie batter into the prepared baking dish. Spread with a spatula or knife to smooth out the top. Top with the reserved ¼ cup of whole mini chocolate eggs.

Bake at 325F for 25-29 minutes, until the edges are browned and a toothpick inserted into the center comes out with moist crumbs. If it comes out with dry crumbs, the blondies are over baked. If it comes out with wet batter, they need more time to bake.

Let the blondies cool in the pan for at least 15 minutes before removing to a cutting board to slice into squares.