I'M A fierce proponent of the quickie dinner. Out of necessity: I have achieved that certain age when it becomes necessary to despense with the preliminaries and leap right into, "Why don't you follow me home and I'll whip up something more comfortable?"
I'm also a seafood devotee: It's less caloric than meat and easier to get away with later in the evening. The following is my favorite way to prepare either scallops or fish, and can be frilled up with various different herbs and spices.
Drain scallops and save liquor. Poach them (or fillets of a firm-fleshed fish) in a mixture of vermouth or white wine and water; bottled onion juice is good, too (unless you're making pilaf on the side, in which it's virtually essential). You can stretch with bottled clam juice, but in moderation. If you have fresh parsley, you may add a few whole sprigs, along with a celery stalk or two and a carrot. If you don't have fresh herbs, shake in a palmful of dried greenery of your choice.
When the seafood is on the verge of being done -- scallops soft and a little resilient, not separating; fish not quite flaking -- drain and set in a warm oven. Strain the poaching liquid and reduce over high heat by about half.
Meanwhile, slice as many mushrooms as you (or a guest) have the strength to, and dice the stems. Melt a couple of tablespoons of butter in a second skillet. Add a chopped onion and saute' until soft but not brown. Add the chopped stems, stir a few times and then add the sliced caps; toss until softened and beginning to sizzle. Squeeze a half a lemon over the mushrooms, toss again and douse with half-cup wine or vermouth. Let that boil down for a minute and then empty the mushroom mixture into a bowl.
Melt 2 more tablespoons of butter in the second skillet and stir in 2 or 3 tablespoons of flour. Stir in scallop liquor, then slowly add the poaching liquid and simmer until thickened. You can add a little heavy cream at this point, or a touch of sherry or madeira or even cognac. Stir in mushroom mixture, heat through and serve the sauce with the poached fish.
This takes only about 15 minutes, and is virtually foolproof. (I "proofed" it just recently while on vacation: At the last minute, discovering that the flour bin was empty, I resorted to a handful of crushed dried rice cereal belonging to my 8-month-old niece, and they ate it anyway.)