Peanut Butter Birthday Cupcakes with Banana Buttercream Frosting

INGREDIENTS

1/4 cup

unsalted butter, softened

1/2 cup

smooth peanut butter

1/2 cup

packed brown sugar

egg

2 tsp

vanilla extract

1 1/4 cups

all-purpose flour

1 tsp

baking soda

1/4 tsp

kosher salt

2/3 cup

milk (I used plain unsweetened almond milk)

ripe banana, mashed (not overripe!)

1/2 cup

unsalted butter, softened

1 tsp

lemon juice

1/2 tsp

vanilla extract

salt

3 cups

powdered sugar

Peanut butter

Finely chopped toasted peanuts