Start by making the shallot chutney for over your fish. Place all the ingredients into a pan and bring to a slow simmer, cook for about 1 hour with a lid on stirring now and again, then remove the lid and continue to cook until most of the liquid has evaporated, which will take approximately another 30 minutes.
Mix olive oil, sliced garlic, salt & pepper, lemon juice and zest, picked thyme leaves and basil and brush the tops of the sardines with this mix.
Slice the tomatoes approximately 1/2cm thick, cutting across the length, place onto a tray and sprinkle with coarse sea salt and milled pepper then drizzle in the balsamic vinegar. Place under the grill to just soften, cooking approximately 3 minutes.
Place the sardines onto a non sticky backing tray and cook under a got grill for approximately 4-6 minutes. Whilst they are cooking toast the sourdough under the grill, brushing with a little olive oil, toasting on both sides till golden in colour. Rub the toast with a little garlic, once the sardines are cooked, spread the chutney over the toast, place on the tomatoes then the remaining basil leaves then the sardines.