In a large skillet or sauté pan, heat the oil over medium-high heat. When it shimmers, add the onion and a pinch of salt and cook, stirring occasionally, until the onion is nicely browned, about 7 minutes. Add the garlic and stir for 1 minute. Add the spice blend and stir for 15 to 30 seconds, until very fragrant and deep brown, then scrape into the slow cooker. Pour
Add more salt, if needed, and stir gently; the sweet potatoes will break up a bit and thicken the stew. Serve.