In a pan, over medium-high heat, add 1/2" of oil. Combine flour, milk, salt and pepper in a bowl, and mix until well combined. Add in onion strips, stirring until all onions are coated. Once oil is warm, add in a thin layer of the battered onions, and fry on each side until brown, about 1 - 2 minutes. Remove and repeat until all onion strips are cooked.