This is another recipe that I could see working with other ingredients of your choice–sweet potatoes, or thinly layered squash would work on top, as would your cheese of choice over the crust. You can substitute up to half whole wheat or white whole wheat flour for the all-purpose. If you don’t have a Smart Oven+, raise the temperature in your oven to 425 degrees.
For the crust:
1 stick (½ cup) unsalted butter, frozen or nearly frozen
1 ¼ cups (155 grams) all-purpose flour
¼ cup (about 1 ounce) finely grated Parmesan or Asiago cheese
½ teaspoon salt
⅓ cup ice water (but you may not use all of it)
For the onions:
1 tablespoon neutral oil
1 tablespoon butter
2 medium onions, any color, sliced into half-moons (about 3–4 cups)
Salt and black pepper
2–3 tablespoons balsamic vinegar
For the rest:
3–4 ounces Parmesan or Asiago cheese, finely grated (about 1 cup), plus more if desired
½ pound Yukon Gold potatoes (about 2–3 small to medium potatoes)
2 tablespoons olive oil
2 tablespoons minced rosemary
1 tablespoon minced garlic
½ teaspoon sea salt or kosher salt (slightly less if using table salt)
Heavy cream or egg for the crust (optional)