Preheat the oven to 400 F. Cut the sweet potatoes in half lengthwise, then place them cut side down on a baking pan lined with parchment paper. Rub the skins with the olive oil and sprinkle with the sea salt. Roast for 40-45 minutes, until tender.
Meanwhile, prepare the braised fennel stuffing. Cut off the stalks of the bulb as well as the hard base of the bulb, then cut the bulb in half lengthwise. In a large skillet of medium-high heat, melt the ½ stick of butter (or non-dairy substitute of your choice). Once the butter begins to foam, add the fennel, placing the cut side down first. Lower the heat to medium and take care that the butter doesn't spatter too much over your stovetop.
Continue cooking the fennel for 15-25 minutes, turning every 5 minutes, until all sides are golden brown and caramelized. Add the stock and bring the liquid to a boil. Cover the pan, lower the heat to a simmer, and cook another 5 minutes. Uncover the pan and continue cooking another 5-10 minutes until the stock is almost evaporated. The fennel should still have some bite but it should be almost cooked through.
While the sweet potatoes are roasting and the fennel is braising, start caramelizing your onions. Very finely chop your onions and add them to a second medium/large-sized pan on your stovetop, together with the tablespoon of olive oil. Cook the onions for 10-15 minutes over medium heat until they soften, then add the garlic and cook for another 5 minutes. Drain the can of chickpeas (or reserve the liquid for some other use) and rinse the chickpeas well. Add them to the pan with the onions and garlic, along with 1 teaspoons of ras el hanout and salt. Continue cooking over medium-low heat until the chickpeas are warmed through.
As the fennel is braising and the onion is softening, drain the mung beans you soaked overnight. Put them in a small saucepan (1 or 2 quarts), cover the beans with cold water, and bring the water to a boil. Continue cooking the mung beans at a gentle boil for 15 minutes, until they are cooked but not soft or mushy. [If you are using a different legume/grain here, simply adjust the cooking time to your grain so it cooks to the same doneness.]
Drain the water from the cooked mung beans and add them to the pan with the chickpea-onion mixture. Taste the mixture for seasoning and add the other teaspoon of ras el hanout plus another pinch or two of salt if desired, remembering that your seasoning here will be combined with the fennel and sweet potato.
Transfer the braised fennel to a cutting board and chop it into smallish bite-sized pieces. Place the braised fennel in a large serving bowl. Add the spiced chickpea mixture to the bowl.
In a small bowl, whisk all the ingredients together to make the spiced date dressing. In another small bowl, use a fork to whisk together the ingredients for the tahini dressing, adding a little more lemon juice or cold water to achieve a pourable consistency (how much you need will depend on your yogurt and your tahini).
Assemble the dish by pouring the spiced date dressing over the fennel-chickpea mixture, then add the freshly chopped cilantro and stir everything together.
Place a half of a roasted sweet potato on each plate, with the fleshy side up, and make a deep cut down the center of each half, squeezing the sides slightly to widen the gap. Spoon a generous heap of stuffing into the hole, then drizzle the stuffing with the tahini dressing.
Serve with a green salad or Israeli "Chik Chak" salad on the side.