Preheat the oven to 190C/180C fan/gas 5.
First,make the dressing. Place all the dressing ingredients in a food processor and blitz until all the shallots are finely diced and a creamy, pale dressing forms. Set aside until ready to serve.
Place the shallots and fennel wedges in a roasting tin and drizzle with 1 tablespoon of rapeseed oil and season with a little salt and pepper. Roast in the oven for 15- 20 minutes until softened but still holding form.
In the meantime, warm the barbecue or heat a griddle pan on the hob. Using a pastry brush, brush all the vegetables with a little oil. Place the leeks cut-side down onto the grill followed by the courgette. Cook the vegetables until they have visible griddle lines, are nicely charred and soft all the way through -this may take a couple of turns on the grill.
When the shallots and fennel are softened, remove from oven and place straight onto the grill. Griddle in the same way as the other vegetables.
Add the vine tomatoes to the roasting tin and place in oven until all the other vegetables have been griddled - approximately 5 - 10 minutes.
Finally,griddle the asparagus for just 2 - 3 minutes.
To serve,neatly pile all the vegetables onto a large platter. Remove the roasted tomatoes from the oven and place on top of the vegetables. Finish with a drizzle of dressing and serve the remaining dressing in a bowl on the side.