Chop the peppers, onions, jalapeño, and mince the garlic. Sauté those ingredients in 1 tablespoon olive oil over medium-high heat for 4-6 minutes until the peppers soften and just begin to brown. Season with salt, pepper, and cayenne. Then remove from heat.
Drain the can of black beans and toss into a large bowl. I like to use a pastry blender to mash some of the beans just to give my filling a different texture, but this is optional. Add the cooked pepper mix to the bowl and stir to combine.
Lightly oil a large, rectangle baking dish. Roll a heaping spoonful in each tortilla and place in the pan, folded edges down. If you have issues with your tortillas breaking, lightly warm for a few seconds in the microwave. Warmed tortillas tend to roll a bit better.
To make the sauce, in a small to medium pot, melt the butter over medium heat. Add the flour and whisk well, making a kind of paste. Slowly add the water and stock, creating a gravy consistency. Remove from the heat and stir in the sour cream. If the mixture is too thick to pour easily, thin with a little more water or stock. Then pour the sauce over the prepared tortillas.
Crumble the cheese over top. And if you had any leftover filling (I had a few tablespoons), toss over the top of everything. Then bake at 350°F for 25-28 minutes, until bubbly and the top begins to brown.
Top with the green onions, cilantro, and chopped avocado. Serve alongside your favorite hot sauce and enjoy!