In a medium saucepan set over medium-low heat, combine sugar, cocoa powder, butter and milk.

Bring to a boil and allow it to boil for 2 minutes.

Remove from the heat and stir in the oats, dulce de leche and vanilla.

Drop by the tablespoonful onto waxed paper. If you prefer, slightly flatten with a spatula or roll into a ball.

Sprinkle each cookie with several grains of sea salt.

Allow to set for at least 1 hour (I found that the texture was the best after the cookies sat out to dry for about 4 hours).