Preheat oven to 350 degrees, then line an 8x8 baking pan with parchment paper.

Whip the butter in a mixing bowl on medium high speed until light and fluffy, around five minutes. Slowly beat in the powdered sugar and vanilla, then stir in the flour and ground pecans.

Turn the dough out into the pan and press gently until the dough covers the entire bottom and is even in thickness.

Bake for 10 minutes.

While the bars bakes, in a small saucepan over medium low heat, add the sweetened condensed milk and chocolate, and stir until melted. Add the vanilla and cinnamon and stir until combined.

When the bars come out of the oven, add the M&M's® Crispy on top, then pour the melted fudge mixture and spread until completely covered. Allow to set in the fridge for 2 hours before cutting.