Preheat oven to 500 degrees F.Advertisement
To prepare vinaigrette: Place 2 tablespoons hazelnuts, vinegar, water and mustard in a food processor or blender; process until as smooth as possible. With the motor running, add 1/4 cup oil in a slow stream through the feed tube until well blended. Add the remaining 2 tablespoons hazelnuts, thyme, 3/4 teaspoon salt and pepper; process for a few seconds more or until the consistency is loose and chunky. Transfer to a small container and stir in shallot.
To prepare salad: Toss Brussels sprouts with oil and salt on a large rimmed baking sheet. Roast until tender, 5 to 7 minutes.
Meanwhile, suprême the oranges: Cut a thin slice off the top and bottom of each. Place on a flat surface. Slice off the peel and white pith below, following the curve of the fruit as you go. Holding the fruit over a large bowl, use a small sharp knife to cut between the membrane and each segment, letting the segments drop into the bowl. Drain any juice from the bowl.
Add the Brussels sprouts to the oranges along with cauliflower, radicchio, apricots and hazelnuts. Drizzle with the vinaigrette and gently toss to combine.
To make ahead: Refrigerate the dressing for up to 5 days.
1 1/2 vegetable, 1/2 fruit, 3 fat