Directions

Begin by making the caramelized onions. Cut both the stem and root ends off the onions and completely peel away the skin. Cut the onions in half, through the roots. Slice the onions into 1/8- inch slices, as evenly and thinly as possible. Heat a large sauté pan over low heat. When warmed, add 2-3 tablespoons of olive oil. When the oil begins to shimmer, NOT smoke, add all the sliced onions and 1-2 tablespoons of butter, Add the sliced onions in 2-3 batches, sprinkling each batch with a bit of kosher salt. Stir to mix the salt into the onions. Let the onions cook slowly over medium-low heat. Turn and stir so the onions cook evenly and become soft and start to brown. This process should take about 30-40 minutes depending on the volume of onions and the size of the pan, etc. Try not to rush the process by turning up the heat and risking burning rather than caramelizing the onions. Monitor the heat so the onions do not stick (if they do stick, a tablespoon of water or stock will loosen the stuck onions from the bottom of the pan). They are ready when they have turned a golden-brown color. Add a pinch of dried thyme and taste for seasoning. Add more kosher salt if necessary and fresh ground black pepper. Set pan aside to

cool, while you build the gratin. The onions can be done in advance and reheated, if necessary, before using. And note, you may have

more caramelized onions than you will need, no worries, they will keep for a few days refrigerated.

Scald the light cream. Put the cream in a small saucepan and bring to a bare simmer. This is ‘scalding’- do not boil the cream or it will likely separate or curdle. Add the prepared mushrooms and a pinch of dried sage and a bay leaf. Set aside to let the flavors infuse.

Peel and thinly, evenly slice the potatoes. Set aside. Don’t worry if they start to brown a bit. I don’t like soaking them in water. Chop half of the package of diced/cubed butternut squash. You are looking for small even chunks of squash, about 2 ½ cups, total. (Reserve the rest of the squash for another dish. Soup?)

Grate the cheeses and combine if using more than 1 kind. Butter the gratin dish. Make sure the oven is pre-heated.

Build the gratin:Overlap one layer of potatoes in the bottom of the buttered gratin dish. Completely cover the bottom of the dish with ‘shingled’ potatoes. Season lightly with kosher salt and a bit of fresh ground black pepper. Scatter small ‘clumps’ of caramelized onions over the potatoes. Scatter ½ of the chopped butternut squash over the onions. Sprinkle 3-4 tablespoons of grated cheese over the squash. Drizzle about 1/3rd of the amount of scalded cream over the top. Build the second layer the same way: sliced potatoes, seasoned with a sprinkle of kosher salt and pepper, spoons of caramelized onion ‘clumps’, chopped butternut squash, grated cheese and 1/3rd more cream. Gently press down the layers with the back of a large spoon.

The final and top layer will be sliced potatoes sprinkled with kosher salt and pepper. Top with grated cheese. Finish by drizzling the rest of the cream all over the top. Cover tightly with foil and bake on a sheet pan (to catch any overflows).

Bake covered for 45-50 minutes.Remove foil. Mix parmigiana cheese and breadcrumbs together and sprinkle over the top. Return dish to oven (uncovered) and continue to bake until top is golden brown and bubbling. And test for doneness by inserting a knife into the dish—it should slide in and out easily.

Let rest for 10 - 15 minutes before serving.