Step 1

Put Oreo Cookies in a food processor and blend until they turn into fine crumbs. Pour in melted butter and pulse a few times until well blended.

Step 2

Line an 8x8 baking pan with foil and lightly coat with cooking spray. Pour cookie crumbs into baking pan and press down into even layer on bottom of pan.

Step 3

Place pan in freezer for 30 minutes while you prepare the cookie dough.

Step 4

In the bowl of a mixer or in a large bowl with a hand mixer, cream butter and sugar on medium speed until light and fluffy, 3-4 minutes.

Step 5

Add vanilla, lemon zest, and salt and blend until combined. Mix in 3 Tbsp sprinkles.

Step 6

With mixer on low, slowly add flour to bowl until well combined. Keep mixer on low and add lemon juice to combine. Then add milk in until dough comes together.

Step 7

Remove pan with cookie crust from freezer and press cookie dough into an even layer over cookie crust.

Step 8

Spread buttercream frosting over the top of the cookie dough and smooth evenly with a spatula. Sprinkle additional sprinkles over the top.

Step 9

Place pan in fridge chill for at least 45 minutes. Once chilled, remove bars from pan by lifting foil. Using a sharp knife, slice into squares.

Step 10

In the bowl of an electric mixer or in a large bowl with a hand mixer or whisk, beat together butter and confectioners's sugar.

Step 11

Mix in vanilla extract and salt. Add a drop of yellow food coloring and mix to combine. If darker color is desired, add another drop.