In a medium sauté pan, set over medium-high heat, heat oil until it begins to shimmer.
Using tongs or a wide spatula, place a tortilla in the hot fat; it should start to bubble immediately; heat tortilla for about 10 to 15 seconds on each side, until soft and lightly browned.
Remove tortilla and set on a rack set over a baking pan, or just on a baking pan if you don’t have a rack; repeat with remaining tortillas, working quickly.
Using a ladle, put about ½ cup chili gravy in the bottom of an 8-by-13-inch baking pan and spread it out a little.
Roll a few tablespoons of cheese into each tortilla; place it seam-side down in the pan, nestling each one against the last.
Ladle chili gravy over the top of the rolled tortillas and sprinkle remaining cheese over the top.
Transfer to pre-heated oven and bake until sauce bubbles and cheese is melted, approximately 10 to 15 minutes.
Remove from oven and sprinkle chopped onions over top; serve immediately.