Sumac and Nigella Seeds Kaiser Rolls with Proscuitto and Provolone Preparation time: 20 mins + rising time Cooking time: 30 mins Makes: 6 rolls INGREDIENTS 1 quantity Basic Rich Babka Dough 1 Tbsp ground sumac 1 bunch thyme, finely chopped 2 egg whites, beaten ¼ cup nigella seeds ½ cup aioli 4 cups baby spinach…