Make or purchase chicken seitan, drain off any liquid, and dice into bite-sized pieces. (Or use 1 cup of butler soy curls rehydrated in 1 cup of vegan chicken broth and fry in 2 tablespoons of neutral-flavored oil for 5 minutes.)
Peel and dice 1/4 cup red onion then place it in a small bowl covered with water and let it sit while you prepare the rest of the ingredients. (This will mellow out the flavor.)
Wash and chop 1/2 cup of celery into small pieces.
Wash and slice 1/2 cup of red grapes into quarters.
Pour the soaked red onion into a colander and rinse with cold water.
Place 2 cups of vegan chicken in a large mixing bowl with 1/2 cup of vegan mayo, 1/2 cup chopped celery, 1/2 cup red grapes, 1/4 cup red onion, 1 teaspoon mustard, 1 teaspoon oregano, 1/2 teaspoon garlic powder, 1/2 teaspoon salt, and 1/4 teaspoon black pepper.
Stir all of the ingredients until well combined and store it in the fridge until you are ready to assemble your sandwiches.
Place about 1/2 cup of the vegan chicken salad sandwich mixture between two slices of bread or toast. (It's also delicious served on lettuce or a vegan bun.)
Make this vegan chicken salad your own! Feel free to omit the onions or red grapes, and add or take away anything that you want.
Use half vegan mayo and half tofu sour cream or plain vegan yogurt to make this sandwich low fat.