A wonderful way to put past-it fruit to good use. This handy guide to shrub making comes from Food52.
Shrubs are a matter of ratio: The sweet spot (the sweet-tart spot, that is) is a 1:1:1 ratio of fruit, sugar, and vinegar. A good place to start for cold process shrub is 1 pound chopped fruit, 2 cups sugar, and 2 cups vinegar; for the heated process, go for 1 pound fruit, 1 cup sugar, 1 cup water, and 1 cup vinegar. Each method should yield about 3 cups of shrub syrup, which will keep in the fridge.
The vinegar:
Most vinegars will work in shrubs, but think about how your fruit will pair with the flavor of the vinegar you select. I would steer clear of plain white vinegar, which is too intensely sharp. Apple cider vinegar is the one I use most, but white or red wine vinegar, rice vinegar, Champagne vinegar, or coconut vinegar also work very well. Balsamic adds an amazing depth to berry shrubs in particular, but you only need a splash. The rest of the vinegar can be cider or wine vinegar.
The sugar:
You can use white or brown sugar; white sugar will really let the fruit flavor shine, while the brown sugar will add another element of flavor. While I haven’t tried this myself yet, you could also experiment with honey, maple syrup, and agave. (Molasses would probably be too overpowering.)
Possible combinations:
strawberries + white sugar + red wine vinegar and a splash of balsamic vinegar
blueberries + thinly sliced ginger + cider vinegar
nectarine + peppercorn + brown sugar + white wine vinegar
peach + cardamom pods + honey + cider vinegar
pear + star anise + brown sugar + white wine vinegar
plum + cardamom + brown sugar + white wine vinegar
For a cold process shrub, assemble your fruit (sliced or mashed gently) in a bowl, and toss it with sugar.
Let this mixture sit, covered securely with a dishtowel, on your kitchen counter for about 2 days. Stir once a day. It should start to look very juicy. After 2 days, strain the mixture into a measuring cup, discard the fruit, then combine the syrup with approximately an equal amount of vinegar (again, your choice, but cider vinegar is a good place to start)—but do this slowly, tasting as you go so that you get a shrub that is just sharp enough for you—especially with a zingier fruit like raspberries or citrus. That's it! Pour it into a jar and stick it in the fridge.
For a hot process shrub, make a simple syrup (equal parts sugar and water) in a medium saucepan over low heat, stirring until the sugar is completely dissolved. Add your sliced fruit and bring the syrup-fruit mixture to a low simmer. Let it bubble away until the syrup has become the color of the fruit and the fruit looks tired. Stir in the vinegar and bring the mixture just to a simmer; strain out and discard the fruit (or serve it over vanilla ice cream), and pour the shrub into a jar. Keep it in the fridge.
Drink up!
Fill a tall glass with ice, pour in a splash of shrub, and top it off with seltzer water, stirring a bit to incorporate the shrub. Or add a shot of booze: I like gin and found it to be delicious with a strawberry-balsamic shrub, but whiskey or vodka would also be delicious. Or do away with the seltzer water altogether and substitute Champagne or another sparkling wine instead.
No matter which process you use, a shrub will keep for a long time in your refrigerator—I would count on a couple of months at least (though I've not yet had one stick around more than a month, so I couldn't say for sure). The shrub should not ferment, bubble, or become slimy. If it does, scold it, throw it away, and start anew.
