Melt butter in a small sauce pan over medium heat. Add onion, cook 3-4 minutes until tender, then add garlic and cook another minute until soft and fragrant.
Add beans, and combine thoroughly so they begin to melt with the onion and garlic.
Once the beans are smooth and melted, add the cayenne and cumin and combine well. Add the sour cream and hot sauce (optional), and stir thoroughly.
for hash browns :
Melt butter in a skillet. Add hash browns and seasonings, stir to mix them together, then cook hash browns according to package directions until browned and crispy.
for eggs :
Heat a small saute pan over medium heat. Whisk eggs, milk, and salt and pepper together. Slowly pour the egg mixture into the saute pan, and use a flat rubber spatula to constantly stir. Once the eggs start to firm up, sprinkle in the cheese. Mix the cheese in until melted, and eggs are "scrambled". Remove from heat.
for burrito :
Warm tortillas in the microwave. Once warmed, spread one layer of creamy black beans onto the middle of each tortilla. Top the beans with eggs, and then top everything with hash browns. Spoon your favorite salsa onto the top of the hash browns, and lift the sides of the tortilla up to meet on top of all of the ingredients. Use a toothpick to pin the tortilla together, and form a "burrito".Serve hot!