For the cupcakes: Preheat the oven to 350 degrees F. Line regular sized cupcake pans with 15 liners.
Mix the flour, baking powder, baking soda
, and salt in a bowl. Set aside. Cream the butter and sugar
together in a bowl until pale yellow. Beat in the eggs and vanilla. Stir in the flour mixture alternating with the sour cream
. Fold in the pureed strawberries
Fill the cupcake liners three-quarters full with batter
and bake until baked through and golden brown, 18 to 22 minutes. Cool completely.
Fill a piping bag with strawberry preserves. Cut the tip of the bag off and insert the tip into the center of a cooled cupcake. Squeeze to allow a small amount of mixture into the center. Release and remove the bag from the cupcake. Repeat on the other cupcakes.
For the frosting: In a mixing bowl fitted with a whisk
attachment, beat the cream and vanilla until fully whipped. Remove from the bowl. In the same bowl fitted with a paddle attachment, beat the cream cheese and confectioners' sugar until blended and smooth. Scrape down the sides and add the whipping cream. Mix until just blended. Fold in chopped walnuts.
To assemble: Generously frost the cupcakes with Cream Cheese Frosting. Enjoy!