Find yourself some halved bones from your local butcher. Place them in a bowl of salt water to bring up to temperature and to leech out some of the blood for at least half an hour (some say to go overnight). After you have done this preheat your oven to at least 350 degrees Fahrenheit but no more than 400 and place the bones marrow-side up inside the oven for 25-30 minutes. During this time arrange your ingredients. You will need whatever amount of pasta you are making, three cloves of garlic (finely chopped), chili flakes (optional), ground black pepper, salt, grated Parmigiano Reggiano and Gruyère cheese. Get your water boiling and in the last seven minutes of cooking the marrow add salt to the water and boil your pasta until just shy of al dente. Remove the pasta from the heat but do not take out of the water. Retrieve a large pan and put it on medium-low heat. Retrieve the bones from the oven (they will be hot). Using a spoon, scrape the bone marrow into the pan, breaking it down with a fork if you have to. Add the chopped garlic until fragrant. Add optional chili flakes. Begin removing the pasta from the pot and putting it directly in the pan. Toss the pasta through so that it is coated in the rendered bone marrow. Add your grated cheese and retrieve some of the pasta water, adding it to the cheese to help melting without clumping. Stirring continuously, toss through the pasta until the cheese melts and forms a sauce. Add more pasta water if it begins to clump. At this point you can add your cooked meats or not. I like leftover steak. Toss it through until heated. Serve.