Crafting the Cookie Base – Preheat oven to 350°F and prepare an 8x8-inch pan with parchment paper. Cream butter and sugar until light and fluffy. Beat in egg and vanilla extract until fully combined. Add salt, baking powder, and flour, mixing until the dough forms. Fold in the crushed Cadbury Mini Eggs. Spread the dough evenly in the pan and bake for 20-25 minutes, or until golden around the edges.

Whipping Up the Frosting – In a large bowl, beat butter and powdered sugar until fluffy. Add milk and beat for another 2-3 minutes until creamy. Slowly add blue food coloring until the desired pastel shade is reached.

Bringing It All Together – Once the cookie bars are completely cooled, spread the frosting evenly over the top. Garnish with extra Cadbury Mini Eggs for a festive touch. Use a warm, clean knife to cut into 9 squares for perfect edges.