Heat a cup of water in a pot and carefully place it in a small bowl - you'll be using this water to rehydrate the ancho chile.
Deseed, remove the stem on the dried ancho chili, then place the ancho chile in the warm-hot water. Allow it to soak for 15 minutes while you prepare the rest of the recipe. Place the garlic cloves, vinegar in a blender. Then carefully remove the ancho chile from the water, and add it to the blender.Blend for 15-20 seconds, or until you have pureed. Pour the ancho chile and garlic mix in a small bowl.
Mix the chile mixture with the mayonnaise with a spatula.
Pour and serve with your favorite snack or burger.