1: To make the burgers, put the turkey, sausage meat, salt, sage, chilli flakes, cayenne pepper, garlic powder and black pepper into a bowl. Work the ingredients together to combine, using your hands, then knead the mixture as you would bread, until it firms up.
2: Dampen your hands a little with cold water. Divide the mixture into 4 portions and form each into a ball, then flatten slightly to make burgers. Place on a plate, cover with cling film and refrigerate for at least 1 hour to rest. You can make the burgers up to 24 hours ahead and keep them refrigerated.
3: Meanwhile, make the slaw. In a large bowl, mix the kohlrabi julienne, onion and flaky salt together and leave to stand for 10 minutes. Tip into a colander and rinse under cold, running water. Pat dry on a clean tea towel or with kitchen paper. Place in a clean bowl and stir in the mayonnaise and mustard, then fold in the chives.
4: Heat a little oil in a non-stick frying pan over a medium-high heat and cook the burgers for about 5–6 minutes each side until cooked through. Or you can grill or barbecue them: first rub the surface of the burgers with a little oil to stop them sticking, then cook for about 12 minutes, turning 2–3 times.
5: Lay a slice of Cheddar on top of each burger and place under a hot grill until the cheese has melted. Serve the turkey burgers with the kohlrabi slaw, pickled green chillies, your favourite condiments and any tasty salad you fancy.