Cook the sausage in a large skillet over medium-high heat until browned all the way through, about 8-10 minutes. Drain.
Turn your slow cooker to HIGH and place the cream cheese in the pot. This will soften your cheese while you cook the meat.
Pour the sausage into the slow cooker, and add the sour cream, Velveeta, Muenster cheese, shallot, Worcestershire sauce, and sage. Mix until well combined.
Cover the slow cooker and cook for 1 hour. Stir. If the Velveeta is completely melted, turn slow cooker to WARM and serve at your leisure. If it is not melted, recover and cook for another 20 minutes and then check again. (There's no reason it shouldn't be melted. If you need to, use a rubber spatula to smush the Velveeta a bit to help incorporate it.)
You can also cook this dip on LOW for 1.5 to 2 hours.If you prefer to bake your dip, follow my Hissy Fit Dip recipe.