Preheat the oven to 350 degrees F.

Make the Crust:  Beat the butter and brown sugar until light and fluffy. Add the flour; mix well. If the dough is still looking dry add cold water a little bit at a time until the dough starts to form. 

Reserve 1/4 cup of the crumb mixture and set aside; then press the remaining crumb mixture into the bottom of an 8 in a square pan. Bake the bottom layer 10 minutes.

Make Cream Cheese Layer: Combine the softened cream cheese, granulated sugar, and vanilla; using an electric mixer, mix at medium speed until well blended.

Add the egg; mix well.

Combine the layers: Layer 1/2 of the M&M candies over the bottom cookie crust; top with the cream cheese mixture.  Spread evenly all over the crust.

Combine the remaining candy and reserved crumb mixture; mix well. Sprinkle the crumb mixture over the cream cheese mixture.

Bake at 350 degrees for about 20 minutes.

Let cool completely before serving.