15 minutes.

I had a lot of fun thinking of good dinners you could make in 15 minutes for our story today. And believe me, I have made a lot of 15-minute dinners. I have often driven home looking forward to something delicious to putter around with, when it turns out that someone in my family has to be at a meeting or practice in--oh-- 15 minutes. Ir I want the family to sit down together, I have to improvise. (I know, they could have made something themselves, but that's another story.)
Here's some things that come in handy, besides leftovers:
Knowing how to make a good cream sauce or bechamel. Cheese sauce on vegetables, tuna sauce on noodles (or toast), creamed hard-boiled eggs or chipped beef, chicken a la king, the basis of broccoli soup or a souffle. I know, it sounds so retro Home Ec, very mid-century WASP. But it's quick--especially if you use instant Wondra flour. The recipe's on the carton. (You simply mix flour, butter and milk together in a saucepan and heat.)

Thin, quick-cooking cuts of meat, a pan sauce and couscous. Couscous is amazing--it takes 5 minutes, even the whole wheat kind. Finely ground bulgur wheat's almost as fast.
I usually make a pan sauce like this: cook pork cutlets or chicken breast slices or turkey or in butter, remove. Add a minced shallot to pan, cook for a few minutes, scraping up any bits from the meat. Add 1/4 cup or so of white wine, let it bubble off, then add 1/2 cup of chicken stock, let it reduce. Even better if you add a 1/4 cup of heavy cream. (approximate measures, of course) Then put the meat back in and let it all heat up together for a minute. But that's just the basics: add mustard, or herbs, or dried fruit, or saute mushrooms with the shallots or use sherry or red wine instead of white. This could be dinner every night and never taste the same.