Preheat oven to 350°F. Line a regular cupcake pan with paper liners or grease with nonstick baking spray.

In a bowl, combine eggs, egg yolks, and 1/2 cup of buttermilk. Set aside.

In the bowl of a stand mixer fitted with a paddle attachment, or in a large bowl if mixing with hand-held mixer, add flour, sugar, baking soda, baking powder, salt, cubed butter and remaining 1 cup buttermilk.

Beat on low speed until moistened, then increase speed to high and beat until light and creamy, about 3-4 minutes, scraping down the bowl once or twice.

Add egg mixture in 2 additions, mixing after each.

Fill cupcake liners no more than 2/3 full. Bake until tops of cupcakes are barely golden and bounce back when gently pressed, 16-18 minutes.

Let cool in pan for a few minutes, than remove to a wire rack to cool completely.

In the bowl of a stand mixer fitted with a paddle attachment, or in a large bowl if mixing with hand-held mixer, add powdered sugar, butter, vanilla and cream. Mix on low until moistened, then increase to high and beat until pale and fluffy, about 5 minutes, scraping down the bowl once or twice.

Brush sides of a piping bag with berry preserves, making anywhere from 2-4 stripes of preserves.

Carefully add frosting to piping bag.

Pipe swirled frosting onto cooled cupcakes.

Cupcakes will keep for a few days at room temperature, but they will hold up better chilled in the fridge.