*You can use hazelnuts or sunflower seeds in place of toasted sesame seeds.
For Dukka: Toast coriander and cumin in a small frying pan over medium heat, stirring occasionally, until aromatic, about 1 min. Let cool. In spice grinder or small food processor, coarsely chop toasted seeds, salt, pepper, thyme and sesame seeds.
For cauliflower: Preheat oven to 425 degrees. In a roasting pan, toss cauliflower, garlic and onion with 3 Tbsp. olive oil. Roast, stirring occasionally, until light golden brown, about 20 min. Add chard stems, toss to coat and roast until tender, about 7 min. Stir in chard leaves, chickpeas, Dukka and remaining 2 Tbsp. olive oil. Roast until chard is wilted, about 8 min. Stir and season to taste with more Dukka and salt.