Preheat the oven to 180 ° C. Peel and cut the sweet potatoes into pieces. Arrange them on the plate, spray them with olive oil, salt and bake for 15 minutes (depending on the size of your pieces). Return to half-cooking.After cooking, let the sweet potatoes cool and let the oven on.If you want to grill your vegetables yourself: wash, dry and cut into thin slices aubergine and zucchini. a baking sheet, spray and salt before baking for 10 minutes turning them half way through cooking. Reserve the grilled vegetables after cooking.During this time, pour in the bowl of the robot chickpeas cooked and chilled, lemon juice, sweet potatoes, 3 tablespoons of olive oil, salt, pepper and spices Mix until you get a creamy texture, add a few spoons of water if necessary. Reserve.Make toast sandwiches, spread a layer of sweet potato hummus, spread the grilled vegetables, the feta cut into pieces, hazelnuts and thyme.