Shaking Beef

Ingredients

• 1 1/2 to 2 pounds beef tenderloin (filet mignon), trimmed of excess fat and cut into 1-inch cubes
• 5 garlic cloves, chopped (about 2 tablespoons)
• 2 tablespoons sugar
• 2 1/4 teaspoons kosher salt
• 1 1/4 teaspoons freshly ground black pepper
• 5 tablespoons canola oil
• 1/4 cup rice-wine vinegar
• 1/4 cup rice wine or white wine
• 3 tablespoons soy sauce
• 1 tablespoon fish sauce
• Juice of 1 medium lime (about tablespoons)
• 2 bunches watercress or 1 small head red leaf lettuce, separated into leaves
• 1 red onion, peeled and thinly sliced (about 2 cups)
• 3 scallions, trimmed and cut in 1-inch lengths
• 2 tablespoons unsalted butter