In a pot at medium heat add sugar, water, butter, salt, vanilla, let butter and sugar dissolve then add flour, let it cook for about 8 - 12 min or till the dough is not sticking to the bottom of the pan (the dough shouldn't be too moisty), turn the heat off and set the pot aside for at least 5 minutes.
Once the dough has cooled a bit, add eggs (one at a time and stir until they are completely integrated), put the dough on a piping bag with a "star" piping tip, and reserve on your fridge, till your oil is hot.
set your oil temperature at 350 F or 180 C and start piping the churros into the oil, a knife or a scissor is handy when you are making churros. let them get golden then set them aside and make a perforate them in the center with a straw.
Put the "dulce de leche" in a piping bag then use a long piping tip to fill your churros and enjoy 'em!