BBQ chicken drummers with green goddess salad

Name: BBQ chicken drummers with green goddess salad
Ingredients: 2 tsp tomato purée; 2 tsp balsamic vinegar; ¼ tsp smoked paprika; 1 pitted medjool date; 1 tsp rapeseed oil; 1 large garlic clove, chopped; 4 large skinless chicken drumsticks; 1 romaine lettuce, shredded; 2 handfuls watercress; 2 chunks cucumber, halved and sliced; 2 jacket potatoes, to serve; 1 small avocado, halved and stoned; 2 tbsp bio yogurt; 1 tbsp lemon juice; 4 spring onions, chopped; ½ tsp dried tarragon; ¼ tsp English mustard powder