With the rack in the middle position, preheat the oven to 170 °C (325 °F). Line a baking sheet with parchment paper.
Lightly seed the tomatoes with your fingers.
In a bowl, combine the tomatoes, potatoes and 30 ml (2 tablespoons) of oil. Season with salt and pepper. Place them flat on the baking sheet. Bake for about 1 hour or until the potatoes are tender but not roasted. Keep warm.
Meanwhile, in another bowl, combine the egg yolk, mustard, lemon zest and lemon juice with a whisk. Pour the oil in a stream, whisking constantly. Add the chives. Season with salt and pepper. Keep refrigerated.
Preheat the grill, setting the burners to high.
Brush the asparagus and oyster mushrooms with the remaining oil. Season with salt and pepper. Place the asparagus on the grill in the opposite direction of the grate.
Grill for 4 to 5 minutes depending on size, rolling a few times with tongs. Grill the mushrooms for 2 minutes on each side. Slice the lobster tails.
On four plates, place the asparagus, tomatoes, and potatoes.
Arrange the lobster tails, then the oyster mushrooms. Drizzle with the dressing. Season with pepper. Serve with fleur de sel.
Recipes with the "Healthy Pick" stamp have been evaluated by a registered dietitian member of the Ordre professionnel des diététistes du Québec.