Prepare an 8x8 pan by lining it with parchment paper.
Place the brown sugar and butter in a large bowl. Mix with a hand mixer until smooth and creamy. (Or use a stand mixer if desired.)
1 cup brown sugar, packed, ½ cup unsalted butter, at room temperature
Add the milk, vanilla, salt and about half the flour. Continue to mix, and as they become combined, add in the rest of the flour until the mixture forms a dough.
⅓ cup milk, 1 teaspoon vanilla, ½ teaspoon salt, 1 ⅓ cups flour
Add the chocolate chips and mix.
¾ cup mini chocolate chips
Place the dough in the prepared pan and press to move the dough to all the edges and corners and create a flat top. Place in the refrigerator for at least 2 hours.
When ready to make the glaze, sift together the powdered sugar and cocoa powder to remove any lumps.
1 ½ cups powdered sugar, ⅓ cup cocoa powder
Add the milk and vanilla to the dry ingredients and mix to combine. Adjust the thickness by adding more powdered sugar to thicken or more milk to thin.
¼ cup milk, ½ tablespoon vanilla
Remove the pan from the fridge and spread the glaze on top. Return to the refrigerator until ready to serve. When serving, lift the dough out of the pan using the parchment paper, then place on a cutting board and cut into 16 square bars.
Notes
The glaze remains a little soft. If you would like the topping to be more of a hard chocolate layer, melt 1 to 1 ½ cups chocolate chips and pour on top of the bars. That topping will set and become firm.
You can substitute water for the milk in the glaze if desired.
Non dairy milk can be used in the bars and/or in the glaze.
If you don't serve these the same day you make them, you can keep them in the prepared pan in the fridge if you cover it with plastic wrap.
Store the cookie dough bars in an airtight container in the refrigerator for up to a week.
These no bake cookie dough bars can be frozen. To thaw, place in the refrigerator at least 24 hours ahead of time.