Peaches, basil, and walnuts make a wonderful trio of flavor and texture. When they meet up with ricotta in this delicious open-faced sandwich, you will get to enjoy a meal that hovers on that very fun boundary between sweet and savory.
American versions of balsamic vinegar are fairly sweet, and if you like a touch (just a dot or a stripe) of this effect on savory dishes, you will enjoy the thick result from reducing the vinegar. You can drizzle this syrup over more foods than you might imagine—from roasted vegetables and grain dishes to mashes and grilled tempeh and tofu. It also works on pancakes, fruit, and sorbet. Store Balsamic Syrup in a covered container at room temperature, where it will keep indefinitely. If it solidifies, just zap it in a microwave for a few seconds, or stir in a little boiling water, and it will soften right up again.
Turn on the stovetop fan and/or open your kitchen windows—the fumes will be intense. Place the vinegar in a small non-aluminum saucepan (a shallow one, if possible) and heat to boiling. Turn the heat down as low as possible, and simmer uncovered for about 20 minutes, or until the vinegar is thick and reduced in volume by about half. (Check it every 5 minutes or so, to be sure it isn’t cooking down too quickly. You don’t want it to go further than slightly more than half its original volume, nor do you want it to burn.)