1/4 cup olive oil
2 red onions, chopped
3 Yukon Gold potatoes, chopped
3 large garlic cloves, peeled and smashed
2 small eggplant, ends trimmed, cut into large chunks
3 small zucchini, ends trimmed, cut into large chunks
4 bell peppers (assorted colors), seeded, cut into large chunks
3 medium tomatoes, seeded, cut into medium chunks
4 portobello mushroom caps, stems removed, cut into large chunks
1/4 cup white wine
2 Tbsp fresh thyme leaves (or 1 Tbsp fresh oregano leaves)
3 Tbsp balsamic vinegar, or more to taste
Kosher salt and fresh black pepper, to taste
2 Tbsp arrowroot or cornstarch