Preheat the oven to 350F (180C). Line the muffin pan with cupcake liners.
Whisk together the egg, the egg yolk, 2 tablespoons of the sour cream, and the vanilla extract in a small bowl or 1 cup glass measuring cup. Cut the butter into 9 pieces. Measure out the frozen raspberries into a small bowl and then return them to the freezer until ready to incorporate into the batter.
Place the flour, granulated sugar, baking powder, and salt in the bowl of a stand mixer. Whisk the ingredients together for about 30 seconds to thoroughly combine the ingredients.
Add the butter and the remaining sour cream to the dry ingredients in the mixing bowl. Mix on low speed with the paddle attachment for about 20 seconds until the dry ingredients are moistened, then increase the mixer speed to medium and beat the batter until it is smooth and creamy, about 1 minute . The batter should be well combined (no lumps of butter). Scrape the sides and bottom of the bowl.
Add the egg mixture in two batches, mixing on medium speed after each addition until the egg mixture is thoroughly incorporated into the batter. Scrape the sides and bottoms of the bowl and mix the batter by hand with a rubber spatula to ensure all the ingredients in the batter are mixed together.
Put the frozen raspberries in a mini food processor and process them for a few seconds until the raspberries are broken down into separate little seeds, called drupelets. If you don't have a mini food processor, place the frozen raspberries in a freezer bag and gently tap them with a rolling pin until they are broken apart into the separate seeds.
Place the raspberries in a small bowl and toss them with 2 teaspoons of flour until the berries are coated with the flour.
Add the berries to the cupcake batter and fold the berries into the batter with a rubber spatula.
Divide the batter evenly between the 12 cups of the muffin pan, about 60 grams each. Each muffin tin should be about 2/3 full. The batter will be noticeably stiffer because the raspberries are frozen.
Bake the cupcakes for 23-25 minutes until they are done in the center. Check for doneness by sticking a toothpick in the center. When you pull it out there should be no or just a couple of crumbs sticking to the toothpick. You can also use an instant-read thermometer. The temperature should be about 205 degrees F.
Remove the cupcakes from the oven and let them cool in the pan for 10 minutes before removing the cupcakes from the pan to a wire rack. Let the cupcakes to cool completely before frosting them.
If making the cupcakes one day in advance before frosting them, store the cupcakes in an airtight container at room temperature.