Preheat oven to 400°F. In a medium bowl, combine vinegar and oil, then whisk in 2 tbsp water. Season with salt and pepper. Add mushrooms to bowl and toss to coat in marinade. Let stand for 10 minutes, turning occasionally.
Preheat a grill to medium-high. Place mushrooms on grill, gill side down, and cook for about 5 minutes, reserving marinade. Add asparagus to marinade and toss to coat. Flip mushrooms over and cook for an additional 3 minutes, until tender. Add asparagus to grill, discard marinade and cook for about 1 minute, until just tender-crisp. (TIP: Be careful not to overcook as asparagus will cook more in the oven.) Chop into ½-inch chunks.
Arrange tortilla chips in a single layer on a large parchment-lined baking sheet. Top with mozzarella, portobellos, asparagus, lobster, Brie and tomatoes. Bake for 10 minutes until cheese is melted and lobster is heated through.
Lobster Thermidor is a creamy cooked lobster mixture that is typically stuffed into the lobster shell for serving – here the mixture tops whole-grain bread slices for a quicker twist on this classic dish.