Preparation

• Slice the top and bottom off an onion. Remove the skin and tough outer layers. Cut the onion in half, lengthwise, from root to tip. Remove the core. Place the flat side on the cutting board, and slice it lengthwise, along the grain, into ¼-inch ribbons. Repeat with the remaining onions.

• Heat the canola oil in a large pot over medium-low heat. Add the onions, salt and pepper. Cook the onions, stirring every 10 to 15 minutes, until they are wilted and the juices are reduced, approximately 1 hour. Lower the heat and stir frequently, scraping the bottom of the pan to ensure the onions don’t stick, until they are dark brown, viscous and sweet, approximately 2 to 3 hours.

• Add the whole-wheat flour and stir to coat the onions. Cook for 2 minutes, stirring constantly. Add the broth, sherry and sherry vinegar. Simmer for 20 minutes, stirring occasionally. Remove from heat, cool to room temperature and refrigerate overnight.

• Before serving, reheat the soup over medium heat. Turn oven to broil. Place the bread slices on a broiler sheet. Brush the tops of the slices with the olive oil, and sprinkle ½ teaspoon of nutritional yeast on each slice. Place the sheet under the broiler for a few seconds to toast the bread, watching carefully to avoid burning. Slice the toasts into triangles. Divide the soup evenly among 6 bowls and garnish with the toasts.

* Available in the bulk-food aisle at Dierbergs and Whole Foods