Thinly slice the onion and garlic.
Heat olive oil in a pan over medium-low heat and sauté the garlic.
Add the onion and cook until it turns translucent.
Pour in the bone broth, milk, and heavy cream, and bring to a simmer.
Break the spaghetti in half and add it to the pan; cook until the pasta is done.
Season with salt and pepper.
Transfer the finished pasta to a plate and garnish with parsley.