Preheat your oven to 350°F (175°C).

Prepare an 8x8 inch baking pan by lining it with parchment paper or greasing it generously.

Melt the butter in a medium saucepan over low heat, stirring until completely melted and slightly bubbling.

Combine the melted butter with brown sugar in a mixing bowl, whisking until smooth and glossy.

Add in the eggs, one at a time, mixing well after each addition.

Sift together the flour, baking powder, and salt in another bowl, then gradually fold this mixture into the wet ingredients until just combined.

Fold in your Mini Eggs gently, ensuring they're evenly dispersed throughout the batter.

Pour the batter into your prepared baking pan, smoothing it out evenly with a spatula.

Bake for 20-25 minutes or until the edges are set and a toothpick inserted in the center comes out mostly clean.

Cool in the pan for about 10 minutes before serving.