Put a pot of water on to boil and cook your macaroni a minute or two shy of the package directions. Drain.
While the pasta is cooking, you can prepare your cornbread mix. Combine flour, cornmeal, sugar, baking powder, salt, and vegetable oil in a mixing bowl and stir to combine. Add in the egg and milk, and stir until everything comes together and there are no lumps. Set aside.
When your pasta is cooked, add it to the bottom of the casserole dish. Spoon and spread your chili over this to cover it all, then sprinkle on the cheese. Finally, carefully spread the cornbread mixture over the top. It will be pretty sticky, so don't worry if it doesn't go exactly to the edge or you have a few small holes.
Bake your chili mac in the oven for 30-35 minutes. Allow to cool for 10 minutes before serving.