In a medium saucepan over medium heat, melt the butter with the brown sugar and lemon juice, whisking to combine. Once melted and combined, slowly pour in the heavy cream, whisking constantly. Once the cream has been incorporated, stop whisking and let the mixture come to a boil. Reduce the heat to medium-low and let boil for 3–4 minutes. Remove from heat and stir in vanilla extract, scotch (if using), and salt. Allow to cool completely. This makes a little over 1 cup of butterscotch sauce, or about 250g.

Preheat the oven to 350°F (177°C). Line a 12-cup muffin pan with cupcake liners. Line a second pan with 3 liners—this recipe makes about 15 cupcakes. Set aside.

In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.

In a large bowl, whisk together the melted butter and brown sugar until combined and no lumps remain. Add the egg, sour cream, milk, and vanilla, and whisk until combined. Add the dry ingredients into the wet ingredients, and stir until combined. Pour/spoon the batter into the liners—fill only 2/3 full to avoid spilling over the sides.

Bake for 20–22 minutes, or until a toothpick inserted in the center comes out clean.

Cool the cupcakes in the pan set on a cooling rack for 10 minutes, then remove them from the pan and place them directly on the rack to cool completely. Cupcakes must be completely cool before filling and frosting.

Using a sharp knife, cut a circle into the center of the cooled cupcakes to create a little pocket about 1 inch deep. The piece you removed will be sort of cone-shaped. Spoon thickened and cooled butterscotch sauce inside each carved-out cupcake—use however much will fit. (Usually you can fit between 1–2 teaspoons of filling in each; you will have butterscotch sauce leftover to drizzle on top of the frosting.) Slice/tear off the pointy end of the “cone” piece of cupcake you removed, and gently press the round piece back on top of the filling. See my How to Fill Cupcakes post if you need extra visuals or help with this step.

Follow the steps to make your frosting of choice. Options include vanilla buttercream (pictured), Swiss meringue buttercream, or even something like not-so-sweet whipped frosting, or light and fluffy whipped cream.

Top each cupcake with frosting (I used a Wilton 1M tip to pipe the frosting) and drizzle with leftover cooled butterscotch sauce.

Store cupcakes at room temperature for up to 2 days or in the refrigerator for up to 4 days. Store any leftover butterscotch sauce in a tightly sealed container/jar in the refrigerator for up to 2 weeks. I recommend a cupcake carrier for storing and transporting decorated cupcakes.