In a large stock pot bring water to a boil, and cook pasta just 2 minutes shorter than package recommendations for al dente time; right before draining, reserve 1 cup of the starchy pasta water; set aside, then drain pasta. In a deep skillet, begin to brown sausage. When sausage is about halfway done, add minced garlic and onions and cook until sausage is browned and crispy and onions are caramelized. Deglaze with vodka and stock. Add tomato paste, diced tomato, salt, and sugar. Increase heat if necessary to reduce liquid by half. When liquid has reduced, add cream, pasta, and starchy water; simmer on medium for 2 minutes, until pasta is tender and sauce has thickened. Garnish with parmesan shavings. Serve immediately.