Vegetarian Portobello Stew

2 1/2 pounds Yukon gold potatoes, cut into bite-sized pieces
2 pounds baby Bella mushrooms (if they are large, cut them in half)
4 large carrots, peeled and cut into bite-sized pieces
2-4 cups pearl onions
8 cloves garlic, peeled and minced
3 sprigs fresh thyme
6 cups vegetable stock, divided
1 cup dry red or white wine
6 tablespoons tomato paste
4 tablespoons Worcestershire
4 tablespoons cornstarch
Kosher salt and freshly-cracked black pepper

Add potatoes, mushrooms, carrots, onions, garlic, thyme, 5 cups vegetable stock, wine, tomato paste and Worcestershire together in the bowl of a crock pot, and gently toss to combine.  Cook on low for 6-8 hours, or on high for 3-4 hours, until the potatoes and carrots are tender.
In a separate bowl, whisk together the remaining cup vegetable stock and cornstarch until combined.  Add to the stew mixture, and gently toss to combine.  Continue to cook for a few minutes, until the sauce thickens up a bit.
Serve immediately.

Source: Gimme Some Oven