Step 1

Place the water and porcinis in a medium heatproof bowl; set aside to soak.

Step 2

Melt the butter in a Dutch oven or large pot over medium heat. Add the onion, celery, carrots, salt, and pepper. Cook, stirring occasionally, until the vegetables are soft and tender, about 8 minutes. Add the barley and cook, stirring occasionally, until lightly toasted, about 3 minutes.

Step 3

Add the flour, stir so it coats the barley and vegetables, and cook for 2 minutes. Add the porcini mushrooms and their soaking liquid (avoid any grit at the bottom of the bowl), cremini mushrooms, and vegetable broth. Bring to a boil, then reduce the heat and simmer until the barley is tender, 20 to 25 minutes.