Israeli sweet potato and lentil fritters with garlic yoghurt sauce

Name: Israeli sweet potato and lentil fritters with garlic yoghurt sauce
Cuisine: Asian, Indian, Middle Eastern
Ingredients: Advertisement; 4 sweet potatoes, peeled and cubed; 1 cup split red lentils, rinsed; 5tbsp olive oil; 3 spring onions, sliced; 1tsp ground coriander; 1tsp ground cumin; 1⁄2tsp ground fennel seeds; 1⁄4tsp ground cinnamon; 2tbsp cornmeal, plus extra to dust; handful coriander, chopped 1⁄2 lemon, juiced; 1⁄4tsp coarse sea salt; 1⁄4tsp freshly ground black pepper; 3⁄4 cup Greek yoghurt; 1 garlic clove, minced; 1tbsp extra virgin olive oil