Combine sour cream and heavy whipping cream in bowl. Set bowl in a larger bowl of hot water to allow cream mixture to reach room temperature. Pour cream into saute pan, warm on low heat. Add sage and marsala, let simmer 5-10 minutes. Add asparagus and walnuts. Simmer another 5-10 minutes to warm asparagus through. Toss with cooked pasta. Garnish with grated Parmesan, if desired.
