For 4 Person(s)
Cook the pasta according to instructions on the package. Drain, toss with olive oil to prevent sticking, and set aside.
Rinse the yellow split peas. Bring 2 cups of broth and 1 cup of water to a boil in a large pot. Add the yellow split peas and cook for 50-60 minutes or until very tender. Drain excess liquid through a fine sieve. Set aside.
Melt the butter in a small skillet over medium high heat; add the onions and sauté for 5-8 minutes or until the onions are very soft and fragrant. Transfer the butter and onions to a blender with the yellow split peas, 1/2 cup broth, and 1/2 cup yogurt. Purée until smooth.
Transfer the sauce back to a pot on the stove over medium low heat. Add the cheese and stir until melted. Add the pasta and stir until combined; season with salt and pepper and serve with a sprig of fresh thyme.