In a large skillet, heat the oil over medium heat, and, when hot, add the mushrooms to the pan and cook, stirring occasionally until the mushrooms have released most of their liquid and are lightly caramelized- about 5 mins.
Add the onion, garlic, ginger, thyme, curry powder, and curry paste to the pan, stirring until spices are very fragrant-- about 1-2 minutes. Season with salt and add the broth, coconut milk, and brown sugar. Bring to a boil.
Add the potatoes, carrots, zucchini, and peas. Cover, reduce heat to medium-low and simmer until vegetables are tender-- about 20 minutes.
Mix the cold water with the corn starch and add to the pan, stirring until thickened. Season with vinegar and cilantro. Serve over rice, topped with toasted cashews and lime wedges.
This recipe was first published on Heather Likes Food in 2010. I've since updated the pictures and made the recipe a bit clearer, but it mostly remained the same.