Beat butter and sugars until creamy, using a mixer. Add in salt, eggs and vanilla. Slowly add flour, baking soda and cocoa, until combined completely. Fold in crushed Oreos and M&M's (batter will be thick).
Press into a parchment paper lined 15x10x1 baking sheet. Bake in a 375 degree oven for 15- 20 minutes, until soft in center and cooked on outside (adjust according to own oven). Remove from oven (will set while cooling).
While baking, heat condensed milk and butter in a small saucepan on medium heat. Stirring constantly with a whisk, add white chocolate to warm milk mixture. Remove from heat and stir until smooth (about 2 minutes).
Pour over cooked cookie bars and sprinkle immediately with crushed candy canes. Allow to set (about 30 minutes). Cut and enjoy!
Notes
Oreos- any variety works great here, original, Christmas, or mint!
M&M's- you can swap these out for holiday chocolate chips, or semi-sweet chocolate chips too.
Cocoa powder- unsweetened cocoa powder is what works here, dark chocolate is best!