Go the full eight minutes when creaming the butter and sugar -- it helps incorporate air and will give the cupcakes a light and fluffy texture.
Preheat oven to 325 degrees. Line two 12-cup muffin tins with paper liners. Whisk together flour, baking powder and salt. Cream butter and sugar on medium-high speed until pale and fluffy, about 8 minutes. Add eggs, one at a time, beating thoroughly between each addition, scraping down sides of bowl as needed. Beat in vanilla. Reduce speed to low; add flour mixture in 2 batches, alternating with sour cream and beating until just incorporated.
Divide batter evenly among the tins using a 1/4 cup measure or ice cream scoop. Tap pans and smooth tops with an offset spatula or the back of a spoon. Bake until a cake tester inserted into the middle comes out clean, about 30 minutes. Let cool on a wire rack, about 30 minutes.
Whisk the jam in a small bowl until smooth. Fold in chopped strawberries. Using a melon baller or teaspoon, scoop out a hole in the center of each cupcake. Fill with 1 to 2 teaspoons strawberry filling. Top with whipped cream and a slice of strawberry. Serve immediately.