When sauteing the mushrooms, arrange them in one layer in the pan, this way they will brown instead of steam. Before serving, sprinkle some truffle salt on top, which adds a lvely earthy character. The truffle salt is completely optional, but if you want to splurge a bit, it is completely worth it.
1. Preheat oven to 350 degrees F. Arrange bread slices into one layer on a baking sheet. Bake in the oven until lightly toasted, about 5 minutes.
2. Using a damp paper towel or clean sponge, brush the caps of each mushroom then remove and discard any hard stems. Slice any small mushrooms into ¼-inch slices and cut the large ones (such as a Portobello mushroom) into large dice.
3. Preheat a large skillet or sauté pan over medium heat. Add a tablespoon of olive oil, and then sauté mushrooms, stirring until golden brown, 5-8 minutes. Sprinkle in a teaspoon of salt, butter, thyme and garlic and sauté, stirring until the butter has absorbed then squeeze lemon juice over the mushrooms.
4. To assemble, spread mascarpone cheese onto each bread slice then top with mushrooms and a pinch of truffle salt and chopped chives.