To prepare the shallots, heat 2 tablespoons oil in a small saucepan over medium-high heat. Add shallots, and cook for 2 minutes or until crispy, stirring constantly. Remove the shallots from pan with a slotted spoon; drain and cool. Set aside.
To prepare salad, arrange watercress and endive on a serving platter. Top with orange sections and avocado. Sprinkle scallops with salt. Heat 1 teaspoon oil in a nonstick skillet over medium-high heat. Add scallops, and cook for 4 minutes, turning once. Spoon scallops over greens mixture.
To prepare dressing, combine the lemon juice and next 4 ingredients (lemon juice through garlic) in a bowl; stir well with a whisk. Heat dressing in a small saucepan over medium heat 1 minute; pour over salad. Sprinkle with mint and shallots.