Chix sandwich on a bagel

From the BBC’s Good Food.com:

Ingredients

• ½ a 400g can chickpea , drained
• 1 small onion , finely chopped
• 1 garlic clove , crushed
• 500g chicken or turkey mince
• 1 small sweet potato (about 100g/4oz), grated
• olive oil , for brushing

TO SERVE

• 12 mini bagels
• 2 tbsp low-fat mayonnaise
• 1⁄4 iceberg lettuce , shredded
• 2 tomatoes , sliced
• 1⁄4 cucumber , sliced