Microwave chocolate squares in a microwave-safe bowl at MEDIUM (50% power) 1 1/2 minutes, stirring at 30-second intervals until melted. Stir until smooth.
Beat 1 cup butter and 2 cups sugar at medium speed with an electric mixer until light and fluffy. Add eggs, 1 at a time, beating just until blended after each addition. Add melted chocolate, beating just until blended.
Add flour, beating at low speed just until blended. Stir in vanilla and chocolate morsels. Spread batter evenly into 2 greased and floured 9-inch tart pans with removable bottoms.
Bake at 350° for 20 minutes or until center is set. Cool completely on wire racks.
Beat 1/2 cup butter at medium speed with an electric mixer until creamy; gradually add powdered sugar alternately with milk, beating at low speed after each addition. Stir in peppermint oil.
Divide butter mixture between each tart, spreading evenly over cooled brownies in pans; cover and chill 1 hour or until firm. Divide Chocolate Glaze evenly between each tart, spreading over chilled butter mixture in pans. Sprinkle crushed peppermint candy around outer edge of each tart.