Start by bringing a large pot of water to a boil and seasoning it with just enough salt to make it taste like a comforting broth. You don't want it too salty here or your risotto will be too salty.
In a large metal skillet with deep sides, heat 1/4 cup olive oil until hot and then add the squash, plus a sprinkling of salt and pepper. Cook, without disturbing too much, until the squash is golden brown all over. Use a slotted spatula to lift into a bowl, hopefully leaving some of the oil behind.
Add a little more oil to the pan to coat the bottom, and now add all of the mushrooms, a little more salt and pepper. Cook until the mushrooms are a deep, dark brown, at least five minutes, shaking every so often. Remove to a separate bowl.
Let the pan cool for a moment, then add another splash of oil and your red onion, plus a sprinkling of salt. Cook the onion until transluscent, then add the rice. Toast the rice along with the onion until thoroughly coated with oil, then add the white wine. Lower the heat so it evaporates at a simmer, not a boil.
Now comes the risotto-making. Add enough seasoned water to cover the rice and control the heat so it's cooking at an active simmer, but not a boil. Continue stirring and cooking like this, adding more water as necessary to keep the risotto covered, for about twenty minutes. About halfway through, start adding the mushrooms and squash to the risotto. Stir and cook, tasting about fifteen minutes in, until the rice is throughly cooked through and creamy and the liquid in the pan has mostly evaporated.
To finish, take the risotto off the heat and add the Parmesan and butter. Stir that in for a minute, ladle into bowls, and top with more Parmesan and a drizzle of either Saba or Balsamic. Serve right away.