This dish was inspired by my desire to create a fun and unusual risotto. Farro is an ancient grain you can find at any grocery store, and it's great to have in your pantry as a substitute for rice. Here, the farro mixes terrifically with the soft Mahon cheese, making a creamy, unique side.
Bring the vegetable stock to a simmer in a stockpot; keep it at a simmer while you prepare the vegetables. Finely dice the yellow onion, carrot, and celery; mince the garlic. In a medium-mesh strainer, rinse the farro under cold running water.
In a medium Dutch oven or wide sauté pan, heat the olive oil over medium-high heat. Add the onion, carrot, and celery, and gently sauté them. After the vegetables have softened slightly, add the garlic. To release the flavors of the aromatic vegetables, add 1 tablespoon of the white wine vinegar. Stir to release the vegetables from the bottom of the pan (a process called "deglazing"). Add the rinsed farro and stir to incorporate. Add the white wine and cook for a few minutes, until the alcohol evaporates.
Season the farro with a generous teaspoon of salt. Start adding the hot vegetable stock, about a cup at a time; gently stir the farro until the vegetable stock is completely absorbed and the grains begin to soften. Add another cup of the hot stock and repeat the process until all the stock has been added and the farro is completely cooked.
Once the farro is creamy and completely cooked, fold in the grated Mahon cheese and stir to combine. Then fold in the cubed butter and add the remaining ½ tablespoon of white wine vinegar; stir to combine. To finish, mince the fresh chives (or fresh thyme, optional) and sprinkle over the top of the dish. Serve immediately.