1. Add the softened unsalted butter to the bowl of a stand mixer fitted with the paddle attachment, or use a large mixing bowl and a hand mixer. Beat on medium speed for 2–3 minutes, until the butter is smooth, pale, and slightly fluffy.

2. Turn the mixer to low speed and gradually add the powdered sugar, about 1/2 cup at a time, letting each addition mostly blend in before adding more. Scrape down the sides of the bowl as needed. When all of the sugar is incorporated, increase the speed to medium and beat for 1–2 minutes until light and fluffy.

3. Add the seedless raspberry jam or thick raspberry puree, vanilla extract, and fine sea salt. Start the mixer on low so the raspberry doesn’t splatter, then increase to medium-high and beat for another 1–2 minutes, until the frosting is evenly pink and very creamy.

4. Pour in 2 tablespoons of the heavy cream or whole milk and beat on medium-high for 1–2 minutes. If you prefer a softer, extra-fluffy buttercream, add the remaining 1 tablespoon of cream and beat again until the frosting is smooth and holds soft peaks.

5. If the frosting seems too soft to pipe, refrigerate the bowl for 10–15 minutes, then beat briefly to restore the creamy texture.

6. Transfer the raspberry buttercream to a piping bag fitted with your favorite tip, or spread it directly onto cooled cakes or cupcakes with an offset spatula. Decorate with the fresh raspberries, placing one berry on top of each of the 12 frosted cupcakes if using.