Tubetti cacio e uova

Boil some tubetti (the small tube-like pasta also known as ditali or ditalini) in well-salted water. When the pasta is done, drain (not too well) and add back to the pot. Mix in a heaping tablespoon of butter or lard per serving of pasta (100g, 4 oz.) and stir until the fat has completely melted. Then add a mixture of egg (1 per serving) beaten with grated parmesan and pecorino cheese (1 spoonful each per serving), a handful of chopped parsley, and salt and pepper to taste. Stir briefly over low heat until the egg has solidified and serve immediately with some additional grated cheese (of either kind) for those who would like it.