Step 1

Trim green tops from 12 oz. radishes (such as red, icicle, watermelon, or daikon); compost or save for another use. Cut radishes into quarters if smaller or into ½" pieces if larger. Transfer to a medium bowl and season generously with kosher salt and freshly ground pepper. Toss radishes with your hands, squeezing lightly to dissolve some of the salt and help the radishes release some juices, 1 minute.

Step 2

Trim top 3" from 6 scallions, then trim root ends; discard. Thinly slice scallions and transfer to bowl with radishes; toss to combine. Set aside.

Step 3

Whisk 2 Tbsp. white wine vinegar, 1 Tbsp. prepared horseradish, and 2 tsp. Dijon mustard in a small bowl to combine. Gradually add ¼ cup extra-virgin olive oil, whisking constantly until emulsified. Season vinaigrette with salt and pepper.

Step 4

Pour half of vinaigrette over reserved radish salad and toss to coat. Divide remaining vinaigrette between 2 plates.

Step 5

Place 2 skinless, boneless chicken breasts (about 12 oz. total) between 2 sheets of parchment paper or plastic wrap. Using a rolling pin or meat mallet, pound chicken breasts out to about ¼" thick. Season both sides with salt and pepper.

Step 6

Heat remaining 3 Tbsp. extra-virgin olive oil in a large skillet over medium-high. Place chicken breasts in skillet and press down firmly on them with a spatula to ensure cutlets are making good contact with the pan. Cook, undisturbed, until chicken is deep golden brown underneath and there is a thick band of cooked flesh around the edge, about 5 minutes. (Cooking the chicken primarily on 1 side ensures great browning but minimizes the chance of overcooking.)

Step 7

Turn chicken over and cook until second side is light golden brown and chicken is just cooked through, about 2 minutes.

Step 8

Transfer a chicken breast to each plate with vinaigrette and let sit 5 minutes for juices to redistribute. Transfer to a clean cutting board and slice each chicken breast crosswise into 4 or 5 pieces. Return to plates. Spoon radish salad over and around chicken, making sure to get all the vinaigrette too.