Put all cupcake ingredients into a bowl and beat for 30 seconds. Scrape down sides of bowl and beat for another 2 minutes.
Fill cupcake pan with liners and divide batter to make 24 cupcakes. Bake according to box directions, or until a toothpick inserted in the middle of a cupcake comes out clean.
Remove cupcakes from pan and cool completely on a wire rack.
Make frosting and decorate
Beat cream cheese and vanilla until smooth. Add dulce de leche and beat until well combined. Add powdered sugar and beat until smooth. Put frosting in a piping bag or zipper bag and store in refrigerator to firm up until ready to use.
When cupcakes are completely cool, snip off the end of the bag of frosting to create a hole approximately 1/2 inch in diameter. Pipe a swirl of frosting onto each cupcake.
Sprinkle frosting with sprinkles of your choice (I used cinnamon sprinkles and chocolate crunchy pearls). Sprinkle with a small amount of fleur de sel or other flaky sea salt.