Radicchio and Apple Salad With Mustardy Croutons

Preparation

1. Step 1

   Preheat oven to 400˚. Place 1 medium leek, trimmed, thinly sliced, in a medium bowl of water and swish around to remove any dirt. Drain and pat dry with a kitchen towel.

   Step 2

   Whisk ⅓ cup extra-virgin olive oil, ¼ cup chopped parsley, 1 Tbsp. Dijon mustard, and 1 tsp. Diamond Crystal or ½ tsp. Morton kosher salt in a large bowl to combine; season with freshly ground black pepper. Add 6 oz. stale country-style bread, torn into 1½" pieces, and toss to coat well. Transfer bread to one side of a large rimmed baking sheet and spread out into a single layer.

   Step 3

   Add leek to oil mixture left in bowl and toss to coat. If leek looks dry, add another 1 Tbsp. extra-virgin olive oil and toss again to coat. Spread out leek on empty side of baking sheet and roast until croutons are golden brown and crisp and leek is tender and beginning to brown, 20–25 minutes.

   Step 4

   Meanwhile, toss 2 small apples, cored, thinly sliced, in 1 Tbsp. apple cider vinegar in a small bowl to coat.

   Step 5

   Whisk 2 garlic cloves, finely grated, 1 cup plain whole-milk Greek yogurt, 1 tsp. Diamond Crystal or ½ tsp. Morton kosher salt, remaining 2 Tbsp. extra-virgin olive oil, and remaining 2 Tbsp. Dijon mustard in another small bowl. Gradually pour in ⅓ cup water, whisking constantly until incorporated. Dressing should be pourable; whisk in a little more water if needed.

   Step 6

   Arrange 2 small heads of radicchio, leaves separated, torn, between 2 platters. Drizzle some dressing over and top with apples, leek, and croutons. Drizzle more dressing over and scatter parsley leaves on top; season with salt and pepper. Serve any remaining dressing alongside.

   Do ahead: Croutons and leeks can be made 3 days ahead. Store croutons airtight at room temperature; cover and chill leeks. Dressing can be made 1 day ahead; cover and chill.