Avocado and prawn cocktail salad

Ingredients

• 250 g cherry tomatoes
• ⅓ cup extra-virgin olive oil
• 2 tbsp buttermilk
• Juice of 1 lemon
• 1 garlic clove, finely chopped
• 1.2kg cooked prawns, peeled, tails on, deveined
• 2 baby cos lettuce, cut into wedges
• 2 Hass avocadoes, cut into wedges
• 1 Lebanese cucumber, cut into ribbons
• Mint leaves and lemon wedges, to serve
• 2 avocadoes, coarsely chopped
• ⅓ cup buttermilk
• 1 garlic clove