Sweet Potato and Black Bean Burritos

My family started doing "Meatless Mondays" a few years ago.  We had quite a few reasons for doing this: economic, health, environmental, and because we like beans.  We also love sweet potatoes. I came across a recipe for sweet potato and black bean burritos in a cookbook.  There were a few things I didn't like about the recipe, so I searched online.  I combined the recipes and added a few of my own twists to it.  It took a few tries, but I finally came up with one that we really like. 
A few notes on this recipe:
1)  If you don't have ground coriander, don't go out and buy it.  The recipe will be just fine without it. 
2) The cheese is optional.  I've had it with and without cheese and love it both ways.
3) Feel free to experiment with the chili powder.  I like to use a combination of traditional and ancho chili powder.
4) These make great soft tacos on corn tortillas.
5) The salsa on top is really important.

Here is the recipe. Enjoy!

Sweet Potato and Black Bean Burritos
4 sweet potatoes, cooked and mashed
1 medium onion, chopped
2 cloves garlic, minced
1 tablespoon olive oil
2 cans black beans, drained and rinsed
2 tablespoons chili powder
1 1/2 teaspoons ground cumin
1 1/2 teaspoons ground coriander
2 1/2 teaspoons prepared yellow mustard
Pinch cayenne pepper
1/2 cup water
2 teaspoons soy sauce
1/2 cup shredded Monterrey jack cheese
6 large, burrito sized flour tortillas

Preheat oven to 350
1) Heat oil large skillet over medium heat.  Saute onion and garlic until soft. 
2) Stir in beans, chili powder, cumin, coriander, and cayenne.  Gradually stir in water and heat until warm.
3) Remove from heat and stir in mustard and soy sauce. Gently mash some of the beans until the mixture thickens.
4) Divide bean mixture, mashed sweet potatoes, and cheese evenly among the tortillas.  Fold the tortillas and place, seam side down on a baking sheet.
5) Bake at 350 for 12 - 15 minutes
6) Top with salsa and sour cream