Prepare the Baking Pan: Lightly grease a 9x13 inch baking pan. Line the long sides with parchment paper, leaving an overhang.

Preheat the Oven: Preheat your oven to 350°F (175°C).

Mix Wet Ingredients: In a large bowl, whisk together melted butter and peanut butter until smooth. Add brown sugar and granulated sugar, whisking until thick and glossy. Incorporate eggs one at a time, then add vanilla extract.

Combine Dry Ingredients: In a separate bowl, whisk together flour, baking powder, baking soda, and sea salt.

Combine Mixtures: Gently fold dry ingredients into wet mixture until no dry streaks remain.

Add Chocolate Chips: Fold in semi-sweet and white chocolate chips.

Transfer to the Baking Pan: Transfer dough into prepared pan and press evenly into corners.

Decorate with M&M’s: Press half to two-thirds of M&M’s into the top and sprinkle with valentine sprinkles.

Bake the Bars: Bake for 18 to 24 minutes, starting to check at 18 minutes.

Add More M&M’s: Press reserved M&M’s into warm bars once out of the oven.

Cool the Bars: Allow to cool completely in the pan for 1 to 1 ½ hours.

Optional Drizzle: Melt white chocolate chips and oil, drizzle over cooled bars, and add extra sprinkles.

Slice and Serve: Lift out using parchment overhang and cut into squares.

Store the Bars: Store in an airtight container at room temperature for up to 3-4 days.