In a large bowl, whisk together the flour and salt. Cut the cold, cubed butter into the flour using a pastry blender or your fingers until the mixture resembles coarse crumbs. Gradually add the ice water, 1 tablespoon at a time, mixing with a fork until the dough just comes together.

Form the dough into a disk, wrap it in plastic wrap, and refrigerate for at least 30 minutes.

While the dough chills, melt butter and olive oil in a large skillet over medium heat. Add the chopped onion and cook until softened, about 5-7 minutes.

Add the shredded cabbage, salt, and pepper. Cook, stirring occasionally, until the cabbage is tender and has released most of its moisture, about 15-20 minutes. Remove from heat and let it cool slightly.

In a separate bowl, whisk together the eggs, heavy cream, and nutmeg.

Preheat your oven to 400°F (200°C). On a floured surface, roll out the pie dough to fit a 9-inch pie dish. Press it into the dish.

Blind bake the crust: Line the crust with parchment paper, fill with pie weights or dried beans, and bake for 15 minutes. Carefully remove the weights and parchment and bake for another 5 minutes until lightly golden.

Spread the cooked cabbage mixture evenly into the pre-baked crust. Pour the egg mixture over the top.

Reduce the oven temperature to 375°F (190°C) and bake the pie for 35-40 minutes, or until the filling is set and the top is golden brown. Let the pie cool for at least 10 minutes before slicing and serving.