Melt butter in large skillet over medium; sauté shallot and garlic 2-3 minutes until fragrant.
Cook mushrooms 5 minutes, stirring occasionally, until starting to release moisture.
Transfer to slow cooker; add wine, thyme, salt, and pepper.
Cover; cook on low 3 hours, stirring halfway, until thick with most liquid absorbed.
Mix in cream cheese and truffle oil until creamy; taste and adjust seasoning.
Transfer to bowl; top with parsley and Parmesan. Serve warm with toasted baguette; keep on warm setting during serving.