Lebanese lamb burgers

Ingredients

• 1 tablespoon cumin seeds
• 1/2 cup (80g) pine nuts
• 800 grams lamb mince
• 1 (150g) brown onion, finely chopped
• 3 cloves garlic, finely chopped
• 1 egg
• 1 cup cooked rice
• salt, freshly ground black pepper, to taste
• 2 tablespoons olive oil
• 1/2 cup (140g) greek-style yoghurt
• 1 tablespoon harissa
• 6 turkish bread rolls, split horizontally
• 6 butter lettuce leaves
• 2 large (440g) ripe tomatoes, sliced thinly
• 1 lebanese cucumber, cut into thin ribbons