Preheat oven to 350º. Line bottom and sides of 8 x 8 pan with foil allowing 2-3 inch over hang. Lightly grease. Melt unsweetened chocolate and butter. Whisk in sugar and eggs one at a time. Whisk in all other ingredients except Hershey’s bars. Pour half into pan, lay candy bars on top and pour other half of mixture over top of candy bars. Bake approx. 45 minutes (may take longer depending on oven). Cool completely. Turn out of pan, pull foil off and dust with powdered sugar. For best results put in fridge for 20 minutes before slicing.