Make sauce: In a medium saucepan, heat oil over medium. Add 1 teaspoon cumin, flour, and tomato paste; cook, whisking, 1 minute. Whisk in broth and 3/4 cup water; bring to a boil. Reduce to a simmer, and cook until slightly thickened, 5 to 8 minutes. Season with salt and pepper, and set aside.
Make filling: In a large bowl, combine 2 cups cheese, beans, spinach, corn, scallion whites, and remaining 1 teaspoon cumin; season with salt and pepper.
Preheat oven to 400 degrees. Lightly oil two 8-inch square baking dishes; set aside. Stack tortillas, and wrap in damp paper towels; microwave on high for 1 minute. Or stack and wrap in aluminum foil, and heat in oven for 5 to 10 minutes. Top each tortilla with a heaping 1/3 cup of filling; roll up tightly and arrange, seam side down, in prepared baking dishes.
Dividing evenly, sprinkle enchiladas with remaining 1 cup cheese, and top with sauce. Bake, uncovered, until hot and bubbly, 15 to 20 minutes. Cool 5 minutes; serve garnished with scallion greens.
Prepare enchiladas through step 3; top with cheese, and cover baking dishes with plastic wrap and then aluminum foil. Place sauce in an airtight container. Freeze enchiladas and sauce for up to 2 months. To bake from frozen: Thaw sauce in refrigerator overnight (or microwave on high 2 minutes, stirring once halfway through). Preheat oven to 400 degrees. Remove foil and plastic wrap from baking dishes, and pour sauce over enchiladas; cover with foil. Bake 30 minutes; remove foil, and bake until bubbly, about 15 minutes more. Cool 5 minutes before serving.