Make sauce: In a medium saucepan, heat 1 1/2 tablespoons oil over medium. Add flour and cook, whisking occasionally, 1 minute. Add broth, chili powder, chipotle and adobo sauce, and 3/4 cup water; bring to a boil, whisking constantly. Reduce heat, and simmer until lightly thickened, about 10 minutes.

Make filling: In a 10-inch nonstick skillet, heat remaining 1/2 tablespoon oil over medium-high. Add onion, garlic, and beef; season with salt and pepper. Cook, stirring, until cooked through, about 8 minutes.

Preheat oven to 350°F. (If freezing, don t place any sauce in baking dish.) Spoon 1/4 cup sauce in bottom of an 8-inch square baking dish. Set aside. Make enchiladas: Stack tortillas; wrap in foil, and warm in oven, 10 minutes. Fill each with a heaping 1/4 cup beef mixture and 2 tablespoons cheese; tightly roll up.

Raise oven heat to 450°F. Arrange enchiladas, seam side down, in baking dish. Top with remaining sauce; sprinkle with cheese. Bake, uncovered, until hot and bubbly, 15 to 20 minutes. Let cool 10 minutes before serving. Serve garnished with cilantro and, if desired, a green salad.