Preheat your oven to 350°F (175°C) and line a baking pan with parchment paper to prevent sticking.
In a large mixing bowl, cream together the softened butter and granulated sugar until the mixture turns light and fluffy, and you can see some gentle ripples forming from the beaters.
Add the eggs one at a time, beating well after each addition to incorporate the eggs fully and create a smooth, slightly thick batter.
Stir in the vanilla extract until combined; your mixture should smell fragrant and look creamy.
In a separate bowl, whisk together the flour, baking powder, and salt to evenly distribute the leavening agents.
Gradually add the dry ingredients to the wet mixture, folding gently with a spatula until just combined, avoiding overmixing.
Gently fold in the mini eggs, distributing them evenly throughout the dough, which will become thick and slightly sticky.
Spread the cookie dough evenly into the prepared baking pan, pressing it into the corners for a smooth, level surface.
Bake in the preheated oven for about 20 minutes, until the edges turn golden brown and the top feels set but still slightly chewy.
Remove from the oven and let the bars cool in the pan for at least 10 minutes, allowing them to firm up and making cutting easier.
Lift the cooled cookie bars out of the pan using the parchment paper and cut into squares or rectangles to serve.
Enjoy these crispy-on-top, chewy-centered bars filled with colorful mini eggs, perfect for sharing or indulging yourself!
