Sweet-potato soup with scented-foam swirl

Instructions

• Preheat oven to 400F (200C). Prick potatoes all over. Place on a baking sheet. Roast until potatoes are tender, 40 to 60 min.

• Scoop potato pulp from skins and place in a food processor. Add ginger. Whirl, while adding some of the broth, until puréed. Pour into a large saucepan. Stir in remaining broth, 1 cup (250 mL) at a time, until as thick as you like. (You may not need to use all of it.) Heat over medium, stirring frequently to prevent scorching, until hot, 10 to 12 min. Spoon hot soup into bowls.

• Meanwhile, pour milk into a 2-cup (500-mL) measuring cup. Stir in cinnamon and nutmeg. Microwave until almost boiling, about 1½ min. Place a whisk in the milk. Holding the handle between your palms, vigorously rub your hands together so it spins back and forth, creating foam. Pour a bit of hot-milk mixture on top of soup in each bowl, holding the froth back with a spoon. Then spoon foam overtop. If foam falls, reinvigorate by whisking.