In a 6-quart slow cooker, combine the onion, mushrooms, potatoes, chiles, Roasted Garlic Mojo, herbs and 1 tablespoon salt. Mix well, spread into a flat layer and pour in the Worcestershire sauce and chicken broth. Lay the chicken thighs on top, skin side up, and sprinkle them with salt. Cover and turn the slow cooker on high. Your Roasted Garlic Chicken will be done in 6 hours, though you can hold it for longer. (My slow cooker can be programmed to switch from high after 6 hours to a "keep warm" temperature for up to another 6 hours. Some slow cookers click to "keep warm" automatically; others need to be switched manually.)
When you're ready to serve, heat your broiler and adjust your rack to the upper third of the oven. Carefully transfer the chicken (still skin side up) to a rimmed baking sheet, pat the skin dry with paper towels, then slide under the hot broiler. In 1 or 2 minutes, the skin should be crispy and browning.
While the chicken is crisping, turn the slow cooker to high and stir in the spinach. When the spinach is wilted (it shouldn't take longer than a minute), taste and season with salt (usually 1/4 teaspoon, depending on the saltiness of your broth.) Divide the mixture among 4 warm deep plates, top with two of the crispy chicken thighs and sprinkle with chopped herbs. Dinner's ready.