Preheat the oven to 200C.
First step: make the sauce. Peel and roughly chop the garlic, ginger and onion and add to a blender along with the rest of the sauce ingredients and blend until smooth.
Finely tear/chop the mushrooms. Peel and finely chop the pumpkin/sweet potato/butternut squash. Chop the sausages into bite sized pieces and slice the leek into nice bite sized rounds (ensuring to give it a good wash as often sediment hides inside the green of the leek). Add all these veg into a large deep oven casserole dish along with the sauce and mix.
Chop the cauliflower into 4 equal sized ‘steaks’ chopping it from the top of it to the bottom. Place the cauliflower steaks on a separate baking tray along with any smaller pieces of cauliflower that fell off and also the cauliflower leaves (chop the wider ones into thin stips so they cook through) and spary/brush with 2 tbsp of oil oil, drizzle over some tamari and sprinkle some coarse sea salt.
Put both trays in the oven and bake for 30-40 minutes or until the pumpkin is soft and cooked through.
Roughly chop the fresh herb of choice.
Remove from the oven and garnish with the roasted cauliflower and chopped fresh herbs.