¼ cup finely diced red onion
4 ounces mascarpone cheese, softened
1 tablespoon fresh lemon juice
1 tablespoon capers
1 tablespoon chopped chives, plus more for garnishing
½ teaspoon kosher salt
½ teaspoon black pepper
8 ounces smoked salmon, slices cut in half the short way
6 cups spring mix salad greens
IN A MEDIUM BOWL, combine the onion, cheese, lemon juice, capers, 1 tablespoon chives, salt, and pepper. Stir until well-combined.
Line a 4-inch-wide × 2-inch-tall round baking pan with plastic wrap. Arrange 8 half-slices of the smoked salmon in the bottom of the pan. Top with the cheese mixture. Arrange the remaining 8 half-slices of smoked salmon on top of the cheese. Cover lightly with plastic wrap. Chill for 10 minutes.
To serve, unmold the timbale onto a plate. Garnish with additional chives. Cut into four wedges. Divide the greens among four serving plates. Serve timbale wedges with greens.