2 to 3 small beets (Note: Since you are roasting beets, you may as well roast a few more. When assembling the tart, I used about 2 heaping cups of diced beets)
Kosher salt and freshly ground black pepper
1 tablespoon unsalted butter or olive oil
1 medium onion, thinly sliced
2 tablespoons dry white wine (or Sherry or Madeira — whatever you have on hand.)
1 recipe tart dough (above)
3 large eggs
¾ cup heavy cream (I used buttermilk)
4 ounces fresh goat cheese (I used less. Add according to taste/preference.)
1 cup chopped walnuts (I used less. Add according to taste/preference.)
1 tablespoon walnut oil (Optional — I did not use.)
About 2 tablespoons chopped fresh parsley