Drain and rinse the black beans. Set them on a paper towel lined plate to dry.
Preheat oven to 400°. Line 8-10 taco shells along a 9 x 13 inch casserole dish and bake for 5 minutes if using a light colored dish, 3 minutes if using a dark dish.
Meanwhile, cook and crumble the ground beef and diced onions over medium-high heat until softened and cooked through, about 8-10 minutes. Drain grease.
Add taco seasoning, undrained diced tomatoes, and beef broth. Bring to a boil and let it reduce for 1-2 minutes, then reduce to a simmer. Stir in the softened cream cheese until melted and combined. By now most of the liquid should have evaporated, with just enough moisture to ensure the meat isn't dry.
Spoon black beans onto the bottom of each taco shell, then top with ground beef mixture.
Top with cheese and bake, uncovered, for 7-10 minutes.
Remove from heat and add desired toppings. Serve!
Notes
Using chicken instead of beef:
3 cups shredded chicken may also be used and seasoned/sautéed on the stovetop as outlined.
I recommend that you cook the chicken over medium heat instead of medium-high, as it can become tough if rapidly cooked/boiled.
Monterey Jack is another great cheese option to combine with or use instead of cheddar.
Refried Beanscan be used in addition to or instead of black beans.
I use Old El Paso Stand 'N Stuff Taco Shells for this recipe. They're nice and thick and can stand up without leaning on each other.