How to Make It
Preheat the oven to 350º and spray two nonstick 6-cavity doughnut pans with cooking oil. In a large bowl, whisk the flour with the baking powder and salt.
In a medium bowl, whisk the eggs with the butter, brown sugar, dulce de leche, milk and vanilla until smooth; add to the flour mixture and whisk until combined.
Spoon the batter into 10 cavities of the prepared doughnut pans until about three-quarters full. Bake for about 16 minutes, until a toothpick inserted in the center of a doughnut comes out clean; let cool slightly.
In a medium saucepan, melt the brown sugar with the butter and salt over moderate heat, stirring occasionally. Bring to a boil and stir in the dulce de leche, milk, corn syrup and vanilla. Boil for 3 minutes, stirring occasionally. Add the confectioners’ sugar and stir until combined.
Dunk each doughnut into the glaze, turning to coat completely. Transfer the glazed doughnuts to a wire rack set over a parchment paper–lined baking sheet and let set before serving.