Instructions. Clean and chop veggies as needed and add to slow cooker along with onion and garlic. Toss with flour to coat well. Slowly stir in broth until well blended with flour. Cover and cook on high for 3-4 hours or low for 6-8. Whisk cornstarch with 1/4 cup water until smooth then stir into the veggie mixure. Stir in cream, cover, and return slow cooker to high heat for about 15 minutes or until mixture thickens slightly. Transfer to a 9×13 baking dish and top with thawed puff pastry sheet (cut to fit if necessary). Melt 2 tablespoons of butter and brush over top of pastry. Bake at 400 degrees for about 10 minutes or until pastry is golden and fluffy. Recipe Notes.