- Rosemary Crust:
- 1 3/4 cups all-purpose flour
- 1 teaspoon roughly chopped fresh rosemary
- salt and ground black pepper to taste
- 10 tablespoons cold butter, cut into cubes
- 1/3 cup ice water
- Sweet Potato-Parmesan Filling:
- 2 pounds sweet potatoes
- 1/2 cup milk
- 1/2 teaspoon olive oil, or to taste
- 1/2 cup butter, softened
- 2 eggs
- 1/4 cup grated Parmesan cheese
- 2 cloves garlic, minced
- salt and ground black pepper to taste
- Pulse flour, rosemary, salt, and pepper together in a food processor until evenly mixed; add cold butter and pulse until mixture resembles coarse crumbs. Drizzle cold water into mixture and pulse until dough comes together. Transfer dough to a bowl and refrigerate, 1 hour to 2 days.
- Place sweet potatoes into a large pot and cover with salted water; bring to a boil. Reduce heat to medium-low and simmer until tender, about 50 minutes. Drain and run cold water over sweet potatoes; carefully remove peels.
- Stir milk and olive oil together in a bowl.
- Beat sweet potato and softened butter together in a bowl using an electric mixer until smooth. Stir milk-olive oil mixture, eggs, Parmesan cheese, and garlic into sweet potato mixture until smooth; season with salt and pepper.
- Preheat oven to 350 degrees F (175 degrees C).
- Roll dough on a floured surface using a rolling pin. Roll dough around rolling pin and press in a pie dish, trimming edges. Pour sweet potato filling into crust.
- Bake in the preheated oven until a knife inserted in the middle of the filling comes out clean, 55 to 60 minutes. Cool pie about 5 minutes before serving.