1. Cook the andouille in a cast iron skillet set over medium heat until browned on both sides, about three minutes a side. They should give off enough fat to cook properly.
2. Add a teaspoon of oil if it looks too dry.
3. Drain the sausage slices on paper towels when done.
4. In a small bowl, mix together the mayonnaise, mustard, and some hot sauce to taste (optional).
5. Spread this mixture on the cut-side of the top and bottom slices of the bread.
6. Divide the cooked andouille between the two bottom slices. Top each with some sliced pickles, onion, and the top slice of bread.