Preparation Steps

• In a saucepan, combine frozen blueberries, granulated sugar, brown sugar, vanilla, and lemon juice. Cook over medium heat, stirring occasionally, until the blueberries release their juices. Stir in a cornstarch slurry to thicken, then remove from heat and let cool.
• Preheat your oven to 350°F (180°C). In a bowl, whisk together the flour, sugar, baking powder, and salt. Cut in the unsalted butter until the mixture resembles damp sand.
• In another bowl, combine vegetable oil, sour cream, milk, eggs, and vanilla, then stir into the dry ingredients until just combined.
• Line a muffin tin with cupcake liners and fill them about ¾ full with the batter. Bake for 15-20 minutes, or until the tops spring back when lightly pressed. Cool the cupcakes in the tin for a few minutes, then transfer to a wire rack to cool completely.
• In a mixing bowl, cream together the unsalted butter and powdered sugar until fluffy. Gradually add the blueberry filling, heavy cream, vanilla, and a pinch of salt, mixing until the buttercream is smooth and creamy.
• Once the cupcakes are completely cool, use a cupcake corer or a small knife to remove the center of each cupcake. Fill the cavity with the blueberry filling, then frost the tops generously with blueberry buttercream. Garnish with a few blueberries on top for an extra pop.