Bistro Beet and Biftek Burgers Tartare

Ingredients

1 large white onion, peeled
2 Tbsp. plus 2 tsp. Grey Poupon Country Dijon mustard, divided use
1 Tbsp. bottled hot horseradish, well drained
2 large egg yolks
2 Tbsp. miso paste
2 1/4 lbs. ground chuck
3 1/2 tsp. coarse or kosher salt, more to taste
freshly ground pepper, as needed
2 Tbsp. plus 2 tsp. salt-packed capers, rinsed and dried, divided use** 1 large bunch watercress, thick stems removed 2 Tbps. chopped
1 1/2 cups shredded peeled beets
2 Tbsp. red wine vinegar
4-5 Tbsp. Colavita Extra Virgin olive oil, or as needed
6 French hard rolls, split*
6 ounce firm-ripe Brie cheese, sliced 1/3" thick
9-10 small French cornichons, drained, sliced lengthwise

Instructions

Prepare a medium-hot fire in the grill; and set rack 5-6 inches from coals, or gas grill's heat rods. Grate 2 Tbsp. of the onions and dice 1/2 cup from remainder. Combine grated onion, 2 Tbsp. mustard, horseradish, egg yolks, and miso, mixing well. Combine with beef, 1/2 Tbsp. salt, 1 tsp. pepper, and 5 tsp. capers, using a light touch. Divide into six 3/4" thick patties, without compacting mixture Chop 2 Tbsp. of watercress; combine with grated beets, diced onion, remaining capers, vinegar, 1 tsp. salt, 1/2 tsp. freshly ground pepper or to taste, and 2 Tbsp. olive oil. Cover and reserve. Brush cut sides of rolls with olive oil. When coals have ashed over, or gas grill is ready, place rolls cut side down until lightly toasted. Set aside. Oil grill rack. Place burgers on rack over direct heat. Close cover, grill 4 minutes without moving burgers, turn and continue to cook until grid-marked and inside registers 160 F. Insert an instant read thermometer through the side to check temperature. Place a slice of Brie on each burger, close cover; cook just long enough to warm cheese. Remove burgers with wide spatula. Divide watercress on roll bottoms, add burgers, and top with beet and onion mixture; add cornichon slices. Close rolls. Serve. *If hard rolls are not available, cut 4" lengths from 2 crusty baguettes. **Salt-packed capers are available in Italian markets and some larger supermarkets. If you use brined-packed capers, rinse them well then pat dry.