Ingredients 

• 1 1/2 Cups (170 grams) Unsalted Butter, at room temperature
• 2 1/2 Cups (400 grams) prepared Dulce de Leche, divided
• 1 teaspoon (5 grams) Vanilla Extract
• Fine Sea Salt, to taste and/or flaky sea salt, for finishing

Procedure

1. In the bowl of an electric mixer fitted with the whip attachment, whip the butter on medium speed until it is very light and fluffy, 4 to 5 minutes. Scrape the bowl well about halfway through whipping. The butter should be lighter in color and visibly aerated. 
2. Add 2 cups (320 grams) of dulce de leche about 1/2 cup (80 grams) at a time, in four additions. Whip the dulce de leche into the butter on medium speed and scrape the bowl well once it’s fully incorporated before adding the next addition. 
3. When the two are fully combined, add the vanilla. If topping with flaky salt, add about 1/2 teaspoon (2 grams) of fine sea salt to the frosting. If you’re not using flaky salt, you can add up to 1 teaspoon (4 grams), or to taste.
4. Transfer to a pastry bag fitted with a large round or star tip. 
5. Using a small (1-inch/2 1/2 centimeter) cookie cutter, the larger side of a piping tip, or a paring knife to cut a small circle of cake out of the center of each cupcake. (Eat this cake for a snack!)
6. Transfer the remaining 1/2 cup (80 grams) of the dulce de leche to a pastry bag and pipe about 2 teaspoons into the center of each cupcake, allowing any excess to form a little dome if it rises above the surface of the cupcake.