How to Make the Ultimate Umami-Bomb Vegetarian Demi-Glace
4 pounds boiling potatoes, such as Yukon Gold, Red Rose or Finnish, peeled and cut into 1-inch chunks
1 tablespoon plus 1/2 teaspoon kosher salt
1/2 cup olive oil
1/2 cup picholine olives
1 tablespoon finely chopped garlic
Freshly ground pepper
Preheat the oven to 400°. In a large saucepan, cover the potatoes with 2 quarts of water. Add 1 tablespoon of the salt and bring to a boil, then reduce the heat and simmer until the potatoes are almost tender, about 20 minutes. Drain the potatoes in a colander and let them dry in their own steam for 10 minutes.
Transfer the potatoes to a rimmed baking sheet and gently toss them with the olive oil. Roast the potatoes in the oven for about 1 hour, turning them every so often with a flat spatula, until golden brown.
Pour off any excess oil in the pan. Scatter the olives and garlic over the potatoes and toss. Lower the oven temperature to 350° and bake the potatoes for 10 minutes longer. Sprinkle them with the remaining 1/2 teaspoon salt and a little fresh pepper and serve piping hot.