1 Preheat the oven and prepare your baking sheets and casserole dish: Preheat your oven to 400°F and line two sheet pans with foil, and lightly grease your 9×13 baking dish.
2 Prep the bread: Tear or cut the bread into bite-size pieces and arrange in a mostly single layer on the sheet pans. Lightly coat the pieces of bread with olive oil, then season evenly with garlic powder, dried ground sage, and black pepper. The oil will help it stick.
3 Toast the bread: Place the baking sheets in the oven, and toast until the bread is golden brown, with some dry edges, about 5 minutes. There is no need to rotate the pans or toss the bread cubes.
4 Whisk your custard: While the bread is toasting, in a large bowl whisk together the eggs, milk, pumpkin puree, turmeric (if using), and salt.
5 Remove the bread and let it cool: Once the bread is toasted, remove it from the oven, and let it cool for 5 minutes. Once the toasted bread has cooled, add 1/2 of it to the egg mixture, stirring to coat. The bread will collapse slightly, then you can then add the rest, stirring to coat.
Set that aside to soak. It won’t be out too long, so you don’t need to worry about covering it.
6 Bake the squash: Add the diced butternut squash to the same foil-lined pan you toasted the bread on and place on the center rack of your oven. Let it roast for 22 minutes, or until golden and tender.
Remove the squash from the oven to cool slightly and assemble the strata.
7 Assemble the dish: Into the 9×13 baking dish, add half the soaked bread and press it down into the dish. Add the roasted butternut squash in a nice even layer, then the kale. Next, add the shredded cheese. Top that with the remaining soaked bread and any liquid in the bowl, pressing that down gently. Sprinkle grated Parmesan cheese evenly over the top. Cover the whole dish with a sheet of foil.
You can refrigerate or freeze the strata at this point and bake it the following day or bake it right away.
8 Bake the casserole: Place the casserole on a baking sheet, then place in the oven and bake for 25 minutes. Remove the foil and continue to bake for 20 more minutes, until the top is crispy and golden.
Serve: When the strata is finished baking, let it cool on the counter for up to 30 minutes, then cut into squares and serve warm or at room temperature.
Leftovers! After it’s cooled, wrap and refrigerate the casserole for up to three days.