Preheat your oven to 200c, fan forced. Line a large baking tray with baking paper or recycle a paper bag as I have here. Place the field mushrooms on the tray. Break off some of the fresh sage and roughly chop up enough for 2 tablespoons. Fill each mushroom with half of the cheese of choice, and then scatter with the thyme leaves and half of the roughly chopped sage leaves. Crumble over the remaining cheese then finish with more sage and a little more thyme.
Now make your salmon crumble by either placing the parsley, walnuts, tarragon, lemon zest, olive oil, salt and pepper in a food processor or in a mortar and pestle (I like to use a mortar and pestle to keep it chunky and for an excuse to smash stuff). Once you have a chunky crumble consistency, place the salmon fillets on the tray with the mushrooms and spoon onto salmon fillets with a teaspoon and roughly press out over the skin.
Finely, place the tomatoes on the tray with the salmon and mushrooms and tear over any remaining sage and thyme leaves.
Before placing in the oven, drizzle everything on the tray with olive oil; especially the mushrooms as they will soak this all up, then season with salt and pepper (especially the tomatoes). Give the tomatoes a toss with the oil and herbs then place the whole tray in the oven for 15 - 20 minutes, depending on your liking regarding the fish. Note you can take the fish out early and then finish off the mushrooms if you would like them done a little more. Basically everything is done when the mushrooms have softened and the cheese has browned, tomatoes blistered and the salmon cooked through to your liking.
To serve, place a portion of salmon and a mushroom on each plate and then divide the tomatoes with all the crispy herbs between them. Finish with another drizzle of olive and freshly chopped parsley.