Put an oven rack in the center of the oven. Preheat the oven to 400 degrees F.
Filling: In a medium saucepan, bring the chicken broth and cumin to a boil over medium-high heat. Remove the pan from the heat and stir in the couscous. Cover the pan until the couscous is tender and all of the liquid has been absorbed, about 5 to 6 minutes. Put the couscous in a large bowl and add the beans, currants, spinach, feta and 1/4 cup olive oil. Season with salt and pepper, to taste. Stir until all the ingredients are combined.
Slice the tops off the peppers and remove all the ribs and seeds. If necessary, cut a very thin slice from the base to help the peppers stand up. Stuff the peppers with the filling and drizzle the tops with olive oil. Put the peppers in an 8 by 8-inch square baking dish. Fill the baking dish with 3/4-inch hot water and bake until the filling is golden and the peppers are cooked through, about 55 to 60 minutes. Cooks
Sauce: In a blender, combine the basil, creme fraiche, olive oil, water, garlic, lemon juice, sugar, salt, and pepper. Blend until smooth. Adjust the seasoning with salt and pepper, to taste.
Remove the peppers from the oven and arrange on serving plates. Spoon the sauce around the peppers and serve.
If the filling begins to brown too quickly, cover the pan with foil.