Preheat the oven to 400 degrees Fahrenheit. Slice the butternut squash in half and remove the seeds. Roast for 45-60 minutes until soft. Let cool for at least one hour.

Once cool, scoop the flesh out and discard the skins. Place the butternut squash flesh into a food processor or high-speed blender and puree for 2-3 minutes, until smooth.

Place 1/2 cup of water in the freezer. Grind the oats into a fine flour in the food processor, then add the flour, salt, and sugar and pulse to combine. Cut the butter into small cubes and add to the food processor; pulse until a fine crumb forms. Slowly stream the cold water in while pulsing, until a smooth dough forms. Place in a container and refrigerate for 1-2 hours.

Once the dough has chilled, dust a clean surface and a rolling pin with flour and roll the dough out into a circle, using your pie pan to help you measure the exact size. Lubricate the pan with butter and transfer the dough to the pan and use a fork to crimp the edges.

Preheat the oven to 350 degrees Fahrenheit.

Combine the butternut puree, sugar, and eggs in a large bowl and beat until well combined and smooth (1-2 minutes with a mixer, 2-3 minutes by hand). Throughly whisk in the salt, spices, and half and half. Pour onto the pie crust.

Bake the pie for 45 minutes. It should be firmly set along the edges and slightly soft in the center when it is done (this prevents the pie from cracking).

Remove from heat and let cool for at least three hours before serving. Store in the fridge.