1. Using a stand or hand held mixer, cream the softened unsalted butter on medium high speed for 3-4 minutes, or until light and fluffy.
2. Lower mixer speed and begin adding powdered sugar, in stages. Add lemon juice, cream, vanilla extract, maple extract and salt. Stop the mixer when needed and scrape down sides of bowl to fully incorporate all the ingredients.
3. Raise mixer speed to medium high and beat until light and fluffy.
4. Adjust the consistency of the maple buttercream frosting by adding either additional cream or more powdered sugar.
5. If desired, add chopped walnuts by folding into the buttercream—or place the nuts between the cake’s layers and on top of the cake.
