Step 1

Preheat oven to 375° F

Step 2

Combine butter with sugar and beat on medium speed until well creamed together.

Step 3

Add the eggs and vanilla extract. Mix into the butter and sugar until the eggs are well beaten.

Step 4

In a separate bowl, combine flour, baking soda and cream of tartar. Slowly add it into batter and beat on medium low speed until well combined and dough forms.

Step 5

Press the cookie dough into a 9-inch by 13-inch pan lined with parchment paper.

Step 6

Bake at 375°F 18-20 minutes. Allow the cookie bars to cool completely.

Step 7

Cut butter into pieces. Using the paddle attachment, whip butter for 5-7 minutes, scraping down the bowl occasionally. Beat until butter look light in color.

Step 8

Add 2 cups powdered sugar and mix on low speed until incorporated into butter.

Step 9

Next Add the heavy whipping cream and mix to combine.

Step 10

Finally add the remaining powdered sugar, and vanilla bean paste and whip it on high for at least 2 minutes until it’s light and fluffy.

Step 11

Spread over cooled cookie bars, slice and enjoy.