It's pretty simple. What you see above is a whole mess of chopped up veggies--carrots, celery, onions, tomatoes, mushrooms, parsley, some garlic--with some soy sauce and peppercorns. Throw them in a pot, cover with water, bring to a boil, reduce to very low simmer, and let cook for at least thirty minutes, more if possible. Bittman doesn't suggest a maximum time but if you've read Michael Ruhlman's The Elements of Cooking, you'll be completely terrified to simmer for anywhere more than an hour (though if you're like me, you probably don't remember the reason he gave). Also taking a queue from Ruhlman, I browned some of the veggies before adding the water for a deeper color and flavor.
Then you just strain, squeezing any excess water and flavor out of the veggies. The broth is delicious: savory with a touch of sweetness. It's very complex. The mushrooms even add a touch of meatiness, without imparting their distinctive--and, for people like my cousin Sara, dealbreaking--mushroomy flavor. You don't taste this and think "mushrooms." I can't wait to see how it works in the dishes I'm planning to make (the lentils, which I cooked beforehand in this stock, were good).