Make the chicken: In a large skillet, heat 1 tablespoon of oil over medium-high heat. Add the chicken and cook until browned and cooked through, about 5-7 minutes. Remove the chicken from the skillet and set aside.
Soften the onion and garlic: In the same skillet, add the diced onion and cook until softened, about 3-4 minutes. Add the minced garlic and cook for an additional minute.
Add the cumin and paprika: Stir in the cumin and paprika and cook for 1 minute.
Add the chicken back in: Add the cooked chicken back into the skillet and stir to combine with the onion and garlic mixture.
Make the sour cream white sauce: In a medium saucepan, melt the butter over medium heat. Add the flour and whisk together to make a roux, cooking for 1 minute. Slowly pour in the heavy cream, whisking constantly to avoid lumps. Bring the mixture to a simmer and cook until thickened, about 2-3 minutes. Stir in the sour cream, paprika, salt, and pepper.
Assemble the enchiladas: In a large baking dish, spread a layer of the sour cream white sauce on the bottom. Arrange 2-3 tortillas on top of the sauce, overlapping them slightly.
Add the chicken and cheese: Spoon some of the chicken mixture onto the center of each tortilla, followed by a sprinkle of cheese (if using).
Roll the enchiladas: Roll the tortillas up tightly and place them seam-side down in the baking dish. Repeat the process until all of the tortillas and chicken are used up.
Top with more sauce and cheese: Pour the remaining sour cream white sauce over the top of the enchiladas and sprinkle with more cheese (if using).
Bake: Cover the dish with aluminum foil and bake in a preheated oven at 375°F (190°C) for 25-30 minutes. Remove the foil and bake for an additional 10-15 minutes, until the top is lightly browned and the cheese is melted and bubbly.