To make the sauce, combine broth, peanut butter, tomato paste, lemon juice, and garlic in a small pan and simmer over low heat 1-2 minutes.
Poke holes all over sweet potatoes with fork. Microwave on high 7-10 minutes, or until soft. Let cool in microwave. (I have cooked them this way, but I prefer to bake the potatoes in the oven at 375 for an hour prior to making - the day before, earlier in the week, whenever I know I can babysit the oven for an hour or so - and briefly reheat them when making this. They taste better & peel more easily.).
Meanwhile, heat oil in large skillet over medium heat. Saute onion 4 minutes or until beginning to brown.
Add chickpeas and saute 2 minutes more.
Stir in spinach, reduce heat to low, and simmer 3-5 minutes or until spinach is wilted.
Scoop sweet potato flesh into bowl and mash with cumin, lemon juice, salt, and turmeric.
Divide sweet potato mixture between two bowls. Top with chickpea mixture and cover with sauce.