Step 1

Arrange two racks to divide the oven into thirds and heat the oven to 425ºF.

Step 2

Peel and dice 2 small sweet potatoes, and transfer to a rimmed baking sheet. Quarter 2 heads radicchio through the core, then cut the core from each piece. Slice each quarter lengthwise into 1/2-inch wide ribbons. Place half in a large bowl, then place the remaining on a second rimmed baking sheet.

Step 3

Drizzle the sweet potatoes with 1 tablespoon of the olive oil, season with 1/2 teaspoon of the kosher salt and some black pepper, and toss to combine. Drizzle the radicchio with 1 tablespoon of the olive oil, season with 1/2 teaspoon of the kosher salt, 1 teaspoon fennel seeds, and some black pepper, and toss to combine. Arrange the sweet potatoes and radicchio into a single layer.

Step 4

Place both baking sheets in the oven and roast until the vegetables are tender and browned in spots, 7 to 10 minutes for the radicchio and 15 minutes for the sweet potatoes. In the last 5 minutes of the sweet potatoes’ roasting time, use a spatula to push the sweet potatoes to one side of the pan, then spread 1/4 cup raw sunflower seeds on the other side in an even layer. The seeds should be deeply toasted at the same time the sweet potatoes become fully tender.

Step 5

Immediately transfer the seeds to a plate and sprinkle with 1/4 teaspoon of the kosher salt. Let the vegetables and seeds cool for at least 10 minutes. Meanwhile, make the vinaigrette and prepare the remaining ingredients.

Step 6

Mince or grate 1 large garlic clove and place in a small bowl. Add the remaining 1/4 teaspoon kosher salt, 2 tablespoons olive oil, 2 tablespoons sherry vinegar, 1/4 teaspoon red pepper flakes, and some black pepper, and stir to combine. Cut 2 1/2 ounces Manchego cheese into small dice (about 1/2 cup), coarsely chop 1 cup fresh parsley leaves and tender stems, and add both to the bowl of radicchio.

Step 7

When the roasted vegetables are warm or room temperature, add them to the large bowl. Drizzle with the vinaigrette and use your hands to toss everything together, making sure everything is coated well. Sprinkle with the sunflower seeds before serving.