Mix together granulated sugar, brown sugar, and cinnamon for the topping.

Preheat oven to 375 degrees with rack in upper third. Line cups of a standard muffin tin with baking cups. Sift together flour, baking soda, baking powder, and salt.

Beat together butter and granulated sugar with a mixer on medium-high speed until pale and fluffy, about 2 to 3 minutes.

Beat in eggs one at a time, then beat in vanilla, scraping down sides of the bowl.

Reduce speed to low, and beat in flour mixture in 3 additions, alternating with sour cream, beginning and ending with flour.

Fold in blueberries.

Divide batter among baking cups and add topping, pressing to adhere to batter.

Bake until golden and a toothpick inserted in center comes out with moist crumbs, about 20 to 21 minutes. Remove cupcakes from tin and let cool completely on a wire rack.

Beat together butter and cream cheese with a mixer on medium-high speed until pale and fluffy, about 2 minutes.

Reduce speed to low and gradually beat in vanilla and confectioners' sugar. Raise speed to medium-high and beat for 1 minute.

Spoon jam on top of icing without stirring, then spoon icing into a disposable pastry bag.

Snip off a 3/4-inch opening in tip and pipe swirled mounds of icing on top of each cupcake.