Step 1

Preheat oven to 375°F. Cut off and discard fennel stalks, reserving some of the feathery tops. Remove any wilted outer layers from bulb; cut a thin slice from base of bulb. Cut bulb into 1/2-inch slices, removing core if desired. Snip feathery tops; set aside.

Step 2

In a 13x9x2-inch baking pan combine fennel slices and onion. Drizzle with oil; sprinkle with 1/2 teaspoon salt. Roast, uncovered, about 25 minutes or just until vegetables are tender.

Step 3

Transfer roasted vegetables to a large saucepan. Stir in broth and potato. Bring to boiling; reduce heat. Simmer, covered, about 10 minutes or until potato is tender. Cool slightly.

Step 4

Transfer vegetable mixture, one-third at a time, to a blender or food processor. Cover and blend or process until smooth. Return mixture to saucepan. Stir in half-and-half, grapefruit juice, and cumin. Cook over medium heat until heated through, stirring occasionally. Season to taste with white pepper and additional salt.

Step 5

Meanwhile, in a small skillet cook fennel seeds over medium-high heat about 3 minutes or until light brown and fragrant, stirring frequently.

Step 6

Top each serving with fennel tops, toasted fennel seeds, and, if desired, Homemade Croutons.