Step 1: Prepare Strawberry Puree & Reduction. Wash and hull 1.5 cups of fresh strawberries. Reserve 1/2 cup for puree and 1 cup for reduction.
Step 2: Make Strawberry Puree for Batter. Place the 1/2 cup reserved strawberries into a food processor or blender and process until smooth (yields about 1/4 cup puree). Set aside.
Step 3: Make Strawberry Reduction for Frosting. Roughly chop the remaining 1 cup of strawberries and place them in a small saucepan over medium heat. Bring to a gentle simmer, mashing with a spoon as they soften. Continue to simmer for 10-15 minutes, stirring occasionally, until the liquid has mostly evaporated and you’re left with a thick, concentrated paste. Let it cool completely.
Step 4: Preheat Oven & Prepare Muffin Tin. Preheat your oven to 350°F (175°C). Line a 12-cup muffin tin with paper liners.
Step 5: Combine Dry Ingredients. In a medium bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt.
Step 6: Cream Butter & Sugar. In a large bowl, using an electric mixer on medium speed, cream together the softened unsalted butter and granulated sugar until light and fluffy, about 3-4 minutes.
Step 7: Add Eggs & Vanilla. Beat in the large eggs one at a time, mixing well after each addition. Scrape down the sides of the bowl as needed. Add the vanilla extract and mix until just combined.
Step 8: Alternate Dry and Wet Ingredients. Gradually add the dry ingredients to the wet ingredients in three additions, alternating with the buttermilk and the prepared strawberry puree. Begin and end with the dry ingredients. Mix on low speed until just combined, being careful not to overmix.
Step 9: Fill Liners & Bake. Divide the batter evenly among the 12 prepared cupcake liners, filling each about two-thirds full. Bake for 18-22 minutes, or until a wooden skewer inserted into the center of a cupcake comes out clean.
Step 10: Cool Cupcakes. Let the cupcakes cool in the muffin tin for 5 minutes before transferring them to a wire rack to cool completely. Ensure they are fully cooled before frosting.
Step 11: Make Strawberry Buttercream. In a large bowl, using an electric mixer, beat the softened unsalted butter on medium-high speed until creamy and pale, about 3-5 minutes.
Step 12: Add Powdered Sugar & Reduction. Gradually add the sifted powdered sugar, one cup at a time, beating until smooth after each addition. Once all sugar is added, incorporate the cooled strawberry reduction and beat until well combined and fluffy.
Step 13: Adjust Consistency & Frost. If the frosting is too thick, add milk or cream one teaspoon at a time until it reaches your desired consistency. If it’s too thin, add more powdered sugar. Frost the completely cooled cupcakes generously. Garnish with fresh strawberry slices, if desired.