Preheat the oven to 350 degrees F. Line an 8x8 inch pan with foil or parchment paper and spray with nonstick spray.
In medium saucepan over low heat, melt butter and chocolate, stirring often. Remove from heat and whisk in sugar and remaining ingredients (except peppermint patties).
Pour half of the batter into the lined baking dish. Then lay the peppermint patties over top of the batter. Top with the remaining batter. Bake for 30 to 35 minutes.
Cool completely, lift the foil out of the pan and onto a cutting board, then slice and serve. Store in a covered container.
Notes
Peppermint Patties are a candy found in the USA. They're a soft peppermint candy dipped in chocolate. Something similar may be used.