Tilapia is my go-to meal for low calorie decadence. It is cheap, cooks quickly and it tastes a lot richer than it is. Not sure if this is small enough for you, but here's one I make a lot when I'm tight on calories in the evening or low on protein:
Set your oven to broil and throw a tilapia fillet (mine are frozen and about 100 calories each) on some tinfoil, add salt and pepper to taste
Tilapia takes just a few minutes to cook, so...
While the fish is cooking, drizzle a tiny bit of olive oil in a small skillet and heat on med-high.
Throw in about 1/4 tsp. (just a pinch) of red pepper flakes
Cook for about 30 sec. to 1 minute
Add about 2-3 Tbsp. of tomato paste, a pinch of salt, and about 1 tsp. dried basil, whisk it around and try to incorporate it into the oil and peppers
Cook for about 1 minute
Add about 2-3 Tbsp. of half and half and whisk into mixture
Cook for about 1-2 minutes, whisking constantly until mixture is smooth
Pour the sauce over the fish and sprinkle shaved parmesan cheese on the top, if desired
For around 200-300 calories (depending on cheese and cream), you've got a really sinful-tasting dinner. Often, I'll wilt a little spinach right into the tomato sauce or I'll serve everything on a little polenta. With a small side of cottage cheese (like 1/4 or 1/3 cup) and a few spears of asparagus, this meal can be done for under 400 calories.
Another great way to prepare tilapia is to poach it in a small skillet with a little water, pepper, 1-2 tbsp white wine and/or lemon juice, some cherry tomatoes, arugula (or spinach) and a tablespoon of capers. If you have the calories to spare, about 1-2 tsp. of butter will really make this dish awesome.