How to Make the Ultimate Umami-Bomb Vegetarian Demi-Glace
8 medium red or fingerling potatoes (about 1 1/2 pounds)
1 shallot, minced
1/3 cup extra-virgin olive oil
Salt and freshly ground pepper
40 tarragon leaves
4 ounces Comté or Gruyère cheese, cut into eight 2 1/2 -inch-square slices
1 tablespoon plus 1 teaspoon aged balsamic vinegar
Preheat the broiler. In a large saucepan of boiling salted water, cook the potatoes until just tender, about 20 minutes. Drain and let cool, then cut each potato into neat 1/3-inch-thick slices.
On an oiled baking sheet, arrange each potato into a round of slightly overlapping slices. Sprinkle each round with a little of the shallot and 2 teaspoons of olive oil and season with salt and pepper. Arrange 5 tarragon leaves on each round and top with 1 slice of cheese. Broil the potatoes, rotating the pan, for about 2 minutes, or until the cheese is bubbly but not browned.
Carefully transfer the potato rounds to plates using a metal spatula. Sprinkle 1/2 teaspoon of the balsamic vinegar around the potato on each plate and serve at once.