Preheat the oven at 350°F.

Combine dry ingredients in a bowl. Set aside.

In a large bowl, cream butter and sugar until light and fluffy.

Add eggs, one at a time, beating well after each edition.

Beat in vanilla extract.

Add dry ingredients and mix well.

Spread two-thirds of the batter in a greased 13"x9" baking pan.

Arrange peppermint patties over top.

Spread remaining batter over patties.

Bake for 35-40 minutes.