In a sauce pan, heat butter (amount your choice—flour should be equal). This makes a roux, or a thickening base for a sauce. Pronounced rue. Cook it gently til slightly brown and until it doesn’t taste of raw flour.
Then you add: sufficient chicken broth (Swansons sells a good one with a good shelf life.)
A mini-can of mild diced chilis (drained.)
Enough sour cream to get it to the consistency you want. Cook a bit, stir.

Form enchiladas by putting cooked (I don’t care how they get cooked, but cooked) chicken bits in a stripe down the middle of a flour tortilla, add cheese of your choice, but mild and white is traditional, then roll, place in pan, and pour white sauce over it all.

Bake at 350 for about 25 minutes.

My source didn’t give amounts, but I’d say if you aim for 2 cups of sauce, enough to handle 4 chicken enchiladas, you want about a third of a cup of roux, of which the flour is the main solid, a half a cup of chicken broth, the chilis, and about a cup of sour cream.

I’m going to try this. I’ve done it without the roux or broth and it’s pretty good, but the rest of the recipe should make it pro.