Roasted sweet potatoes with chipotle black beans

Name: Roasted sweet potatoes with chipotle black beans
Ingredients: 2 large sweet potatoes (or 4 small); 1 tsp vegetable oil; 400g tin black beans, drained and rinsed; 2 tbsp olive oil; 2 garlic cloves, finely chopped; 100g/3½oz roasted peppers from a jar, drained; ½ tsp smoked ground paprika; 1 heaped tsp chipotle chilli paste (from a jar); 150ml/5½oz just-boiled water; 200g/7oz Greek-style yoghurt; ½ lime, juice and zest; 150g/5½oz cherry tomatoes, quartered; 2 spring onions, sliced diagonally; 1 heaped tsp pickled jalapeño slices; ½ lime, juice only; 2 tsp olive oil; fresh coriander, to garnish (optional); salt, to taste