1Preheat oven to 350 degress line eighteen 2 1/2 inch muffin cups with paper liners, set aside. Combine flour, baking powder and soda, and 1/4 teaspoon salt, set aside.
2In large bowl beat butter with electric mixer on medium to high for 30 seconds. Add sugars, beat until well combined. Beat in molasses and vanilla.
3Alternately add flour mixture,buttermilk, and cream soda to butter mixture, beating on low speed after each addition until combined. Stir in 1/2 cup of the toffee. Fill cups 3/4 full.
4Bake about 18 minutes or until tops spring back when lightly touched. Cool in pans on racks 5 minutes. Remove from pans cool. Frost then top with remaining toffee.
For the brown butter, in saucepan heat 1/4 cup butter over medium -low heat until lightly browned, about 8 mintues, cool.
6In bowl beat 1/4 cup softened butter with mixer on medium 30 seconds. Add cooled brown butter, heat until combined. Add powdered sugar,and vanilla,nutmeg and salt. Beat in 1 to 2 tablespoons buttermilk until spreadable. Use immediately. If frosting begins to set up, stir in a small amount of boiling water.