Remove the tomahawk steak from the fridge around an hour before you are ready to start. Preheat the oven to 80°C (176°F) (top/bottom heat) and pre-cook the steak in the middle of the oven for approx. 20 minutes until it reaches a core temperature of 52 degrees Celsius. In the meantime, wash the potatoes and prick them several times all over with a fork. Season the potatoes and wrap them in greased aluminium foil. Bake the potatoes for 60 minutes in the oven at 200°C (392°F) (top/bottom heat) or above the glowing coals on the BBQ.
For the mixed vegetables: wash and dry the courgette, aubergine and bell pepper. Halve the pepper and remove the centre. Chop the vegetables into bite-sized pieces. Brush the mushrooms clean and slice them into quarters. Peel the onion and the garlic. Cut the onion into quarters and slice the garlic. Wash and dry the thyme and shred the leaves. Grease the oven-proof dish with olive oil. Mix the rest of the olive oil in with the vegetables, thyme and chilli flakes and season with salt and pepper.
Arrange the vegetables in the oven-proof dish and roast for approximately 15 minutes, stirring occasionally. In the meantime, mix together all the ingredients for the dip and season to taste. Cook the tomahawk steak briefly on both sides on the hot BBQ to give it a nice colour and grill lines. Then slice it and season to taste with coarse salt flakes and steak pepper. Slice open the wrapped jacket potatoes lengthways and gently ease them apart a little, then garnish with the dip.
Serve with the vegetables.