Preheat your oven to 350°F (175°C). Line a 12-cup muffin tin with cupcake liners.
In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.
In a large mixing bowl, cream the softened butter and granulated sugar until light and fluffy, about 3-4 minutes.
Add the vanilla extract and mix until combined.
In a separate bowl, combine the whole milk and dulce de leche, stirring until smooth.
Gradually add the dry ingredients to the butter mixture, alternating with the milk and dulce de leche mixture. Start and end with the dry ingredients, mixing until just combined.
Fold in the remaining 1/2 cup of dulce de leche until swirled through the batter. Do not overmix.
Divide the batter evenly among the cupcake liners, filling each about two-thirds full.
Bake in the preheated oven for 18-20 minutes, or until a toothpick inserted into the center comes out clean.
Remove the cupcakes from the oven and let them cool in the pan for 5 minutes before transferring to a wire rack to cool completely.
While the cupcakes are cooling, prepare the frosting by whipping the heavy cream and powdered sugar in a large bowl until stiff peaks form.
Once the cupcakes are completely cool, use a small knife to cut a cone shape from the top of each cupcake, creating space for the filling.
Fill each cupcake with a teaspoon of dulce de leche, then replace the cone on top.
Frost the cupcakes with the whipped cream mixture, and drizzle additional dulce de leche over the top before serving.