For a crowd-pleasing Christmas treat, look no further than these chewy chocolate toffee cookie bars. Studded with red and green M&M's, these holiday bar cookies are a cute, festive treat.

There should be about 1 1/2 cups of toffee pieces. For the cookie bars: Preheat the oven to 350°F. Line a 13-by-9-inch baking pan with parchment paper, letting the excess extend over the sides of ...