Grilled Salmon Burgers with Avocado and Butter Lettuce

Ingredients

• 1 ½ lb skinless, boneless salmon
• 2 tsp Dijon mustard
• 1 tbsp mayonnaise
• 1 ½ tsp <a href="/products/weber-gourmet-burger-seasoning">Weber® Gourmet Burger™ Seasoning</a>
• ½ cup coarse breadcrumbs
• 1/4 cup scallions, sliced (white and green parts)
• 1 tbsp olive oil
• 4 buns
• 1 ripe avocado, pitted and thinly sliced
• 1 beefsteak tomato, sliced into 4 rounds
• Butter lettuce leaves