Sweet Potato and Wild Rice Burgers with Green Tahini Dressing

Name: Sweet Potato and Wild Rice Burgers with Green Tahini Dressing
Ingredients: 4 medium sweet potatoes, about 1kg; 3-4tbsp olive oil; 6 spring onions, finely sliced; 250 g pouch microwavable wholegrain basmati and wild rice; 125 g fresh white breadcrumbs; 2 tsp. fresh thyme leaves; 1 tsp. ground cumin; 6 tbsp. tahini; large handful flat-leaf parsley, roughly chopped; juice 1 lemon; 1 small garlic clove, crushed; 6 ciabatta rolls (or vegan burger buns), split; 2 avocados, peeled, stoned and sliced; 200 g cucumber, sliced; 50 g rocket