Heat treat the flour by placing it in a microwave safe bowl, and microwaving in 30 second increments, stirring each time, until the temperature reaches a temperature of 165 degrees (about 2 minutes total). Allow to cool.
Using an electric mixer, or a stand mixer with the paddle attachment, cream together the butter, sugar and brown sugar. Add in the peanut butter and vanilla and mix until smooth.
Mix in the flour, then stir in the oats and the M&Ms. Press the dough into a parchment lined 2 quart baking dish.
Pour the heavy cream into a microwave safe bowl with the chocolate chips, and microwave in 30 second intervals, whisking each time, until the chocolate chips have melted and the mixture is smooth and shiny.
Pour the chocolate ganache over the prepared cookie dough and spread to the edges. If desired, sprinkle the mini M&M's over the top of the chocolate.
Chill for 1 to 2 hours until set.
Notes
Calories are automatically generated. For best results calculate based on your exact ingredients.