Preheat oven to 350 degrees F. Lightly grease 9 x 13 inch pan or line with parchment paper.
2. In large bowl, add in melted butter and light brown sugar. Blend with electric mixer on medium speed for 3 minutes.
3. Add in eggs, one at a time followed by vanilla extract. Continue to blend on medium speed until well-blended.
4. Add in flour, baking powder, and salt and blend on medium-low speed just until ingredients are combined.
5. Fold in semi-sweet chocolate chips, marshmallows, M & M candies, and chopped Cadbury mini eggs.
6. Spread batter evenly throughout prepared pan. Bake at 350 degrees F for 30 to 35 minutes or until edges are light golden brown.
7. Remove pan to wire rack to cool for at least 10 - 15 minutes. Cut into squares.