Preheat the oven to 425ºF. Line a baking sheet with parchment paper. Toss the butternut squash cubes with the olive or avocado oil and salt, and spread out in a single layer on the lined sheet.
Roast for 30 to 40 minutes, stirring once halfway through.
Heat the ghee in a large skillet over medium to medium high heat. Add the onion and cook for about 3 to 5 minutes, until soft.
Add the ground sausage, breaking up and cooking until browned.
Add the chopped apple, chestnuts, and kale, and cook for a couple of minutes to soften. Add the salt, pepper, garlic, and herbs. Continue cooking for a couple of minutes, allowing the flavors to combine.
Add the roasted butternut squash to the sausage mixture and stir to combine. Transfer the entire mixture to a baking dish (or leave it in the skillet if ovenproof). Pour the whisked eggs over top, and lightly mix.
Lower the heat to 375ºF. Bake for 30 minutes or until browned on top and eggs are set.
Serve hot!