Place porcinis in a bowl and cover with boiling water; let sit until softened, about 30 minutes. Using a slotted spoon, transfer mushrooms to a cutting board and finely chop. Pour soaking liquid through a fine-mesh sieve into a bowl, discarding any dirt or sediment. Set mushrooms and soaking liquid aside.
Heat oil in a 6-qt. Dutch oven over medium-high. Add gar