Heat milk, cream, water, salt, and pepper in a large pot. Whisk in cornmeal; keep stirring while the mixture slowly simmers and thickens (approximately 15 minutes). Add butter, whisking until melted, then cheese until fully incorporated.
Toss lemony arugula with olive oil; season with salt and pepper (to taste).
Serve equal portions of polenta in bowls, topped with RSS Organic Lemony Arugula.