Preheat the oven to 350°. Spray 9x9 baking pan with nonstick cooking spray and line pan with parchment paper.

In a large mixing bowl, beat butter and sugar together on medium-high speed until light and fluffy. Add the egg and vanilla; beat until blended. Add flour and salt and mix on low speed just until blended. Spread the dough into the prepared pan. Bake for 10 minutes.

Remove from the oven and allow to cool for 5 minutes. Layer the toffee bits, chocolate chips, coconut, and pecans evenly over the crust. Drizzle the sweetened condensed milk evenly over the entire surface of the bars. Finish with a layer of M&M’s on top.

Bake 35 to 45 minutes or until top is bubbly and a deep golden brown over the entire surface. Remove from oven and allow to cool completely in the pan before cutting.