Take noodles. Anything without a lot of nooks and crannies works. I'm fond of long flat noodles, purely for the way they look. Cook them.
Mix up peanut butter (unsweetened chunky is best, but anything works) with water or coconut milk until it is creamy. Add a teaspoon (or more) of chili sauce for heat. Pour this over the drained noodles, and stir. If it's grainy and dry, add more water or coconut milk. If it's too thin, you can mix in more peanut butter, but it's hard.
Sprinkle with chopped green onions.
Variations: Toasted unsalted peanuts are nice. As are toasted sesame seeds. You could also use grated carrots or finely sliced celery. Meat or tofu could be added as well. Green beans are lovely in the sauce as well.
Garlic or ginger could be added to the sauce.
Reheating - I usually add a bit of water since the sauce can get too dry and grainy if you don't. Excess sauce can be chilled, but not frozen. The noodles are quite edible cold.