1/4 to 1/2 cup heavy cream
1 t. red pepper flakes (or more to taste)
salt and pepper to taste
1 12 oz package of bacon or about 8 slices, diced
1/2 cup diced onion
While the pasta is cooking, whisk together the eggs, cream, red pepper flakes, salt and pepper. Set aside.
Brown the onions and bacon together until done. Drain all but about 2 T of drippings. When the pasta is finished, drain it and immediately return it to the hot pan. Pour the bacon/onion mixture over the pasta. Pour the egg/cream mixture over the pasta and toss it together until coated. The hot pasta is what sets the eggs. Sprinkle with Parmesan and parsley if that floats your boat and serve.
You can also add 1/4 cup of butter to the pasta when you add the egg mixture. I cook the bacon and onions together because I think it gives a better flavor. I also leave some of the bacon drippings in because of the flavor and, let's face it, this isn't a recipe you make when you're looking to count calories anyway. So, why skimp?
As far as the eggs go: you want at least 1 egg for every 100 g of pasta, so a one pound box of pasta would take 4 eggs. Traditionally, you'd probably do about 1 cup of dry pasta per person, so a 1 lb box is about 4 cups. I usually use 1/2 a box of mini pasta and 4 eggs anyway. It's creamier that way.