Blueberry Cupcakes with Butter Cream Frosting

3 1/4 cups all purpose flour
1 1/4 cups sugar
1 tablespoon baking powder
1/2 teaspoon coarse kosher salt
1/4 teaspoon baking soda
6 tablespoons unsalted butter, melted
1/4 cup canola oil
2 large eggs
1 cup buttermilk
1 cup whole milk
1 teaspoon vanilla extract
1 teaspoon grated lemon peel
1 1/4 cups fresh blueberries, frozen for 4 hours


2 1/4 cups powdered sugar
10 tablespoons unsalted butter, room temperature
1/2 teaspoon coarse kosher salt
1 1/4 teaspoons vanilla extract
4 teaspoons (or more) whole milk
1 cup chilled fresh blueberries
Fresh mint sprigs (optional)

Preheat oven to 350°F.
Line two 12-cup muffin pans with paper liners. 
Sift flour and next 4 ingredients into large bowl. 
Whisk melted butter and oil in medium bowl. 
Add eggs; whisk to blend. 
Whisk in buttermilk, milk, vanilla extract, and peel. 
Add buttermilk mixture to dry ingredients; whisk just to blend. 
Stir in frozen blueberries. 
Divide batter among liners.
Bake cupcakes until tester inserted into center comes out clean, about 23 minutes. 
Transfer cupcakes to racks; cool.
For Frosting:
Combine first 4 ingredients in medium bowl. 
Add 4 teaspoons milk. 
Using electric mixer, beat until well blended and fluffy, adding more milk by teaspoonfuls if dry, about 4 minutes. 
Spread frosting over top of cupcakes.
Garnish cupcakes with chilled berries, and mint sprigs, if desired.