Step 1

Stir together the shallots, vinegar, salt, sugar and pepper in a small bowl. Slowly whisk in the olive oil until well combined. Set aside for at least 30 minutes for shallots to mellow.

Step 2

Heat a charcoal or gas grill to moderate heat. Grill the sliced squash, flipping when grill marks appear and the squash has softened slightly, 7 to 8 minutes per side. Remove from the heat and arrange in a shallow serving dish. Cover tightly with aluminum foil to keep warm and let steam, covered, for 10 minutes.

Step 3

Spoon the vinaigrette over the grilled squash, then garnish with the chopped chives. Serve warm.