Preheat your oven to 350°F (175°C).
Grease and line a baking tray with parchment paper. Use a baking tray approximately 9x13 inches for the perfect thickness.
In a large bowl, whisk together the melted butter and brown sugar until well combined.
1 Cup Butter, 2 Cups Light Brown Sugar
Add the eggs, one at a time, beating well after each addition. Stir in the vanilla extract.
2 Large Eggs, 1 Tablespoon Vanilla Extract
In a separate bowl, whisk together the flour, baking powder, and salt. Gradually add the dry ingredients to the wet ingredients, stirring until just combined.
2 Cups All Purpose Flour, ½ Teaspoon Baking Powder, ¼ Teaspoon Salt
Gently fold in the white chocolate chips, semi-sweet chocolate chips, red and green smarties or M&Ms, and red and green sprinkles, reserving a handful of chocolate chips, smarties, and sprinkles for topping.
¾ Cup White Chocolate Chips, ¾ Cup Semi Sweet Chocolate Chips, ¾ Cup Red & Green Smarties or M&Ms, 2 Tablespoons Red & Green Sprinkles
Spread the batter evenly into the prepared baking tray. Sprinkle the reserved chocolate chips, smarties or M&Ms, and sprinkles on top.
Bake in the preheated oven for 25-30 minutes or until the edges are golden, and a toothpick inserted into the centre comes out with moist crumbs but not wet batter.
Allow the bars to cool completely in the tray before cutting into desired sized pieces. Enjoy! :)