Preheat oven to 350 degrees F.
In a small mixing bowl add ketchup, spicy brown mustard, and mayo. Mix and set aside.
In a 9 x 9 baking pan add the bottom half of your buns. Add 1 tablespoon of sauce and spread. Add the Gardein patty, cheese, and pickles. Top with one more tablespoon of sauce and place the top of your bun.
Bake for 15 minutes or until warm and cheese has melted.