Taken from my recipe Bible, aka Deborah Madison's Vegetarian Cooking for Everyone.
2 1/2 lb winter squash (eg butternut)
1 small head garlic, cloves separated but not peeled
1 tbs olive oil, plus extra for the squash
1 onion, finely diced
12 fresh sage leaves, chopped, or 2 tsp dried
1/2 cup freshly grated pecorino or Parmesan
salt and pepper
1 egg, beaten
Yeasted Tart Dough, recipe to follow.
Make the dough. Preheat oven to 375. Cut squash in half, scrape out seeds, brush cut surface with olive oil. Stuff garlic into the cavities and place the squash cut side down on a sheet pan. Bake until flesh is tender, about 40 min. Scoop out squash and squeeze garlic cloves. Mash them together with a fork until fairly smooth, leaving some texture.
Warm 1 tbsp olive oil in a skillet over med heat. Add onion and sage and cook until onion is soft and beginning to color, about 12 min. Add it to the squash along with the grated cheese and season with salt and pepper to taste.
Roll out the dough into a 14 inch round and spread filling over it, leaving a border of 2 inches or more. Pleat the dough over the filling, then brush the edges with beaten egg. Bake until the crust is golden, about 25 min.
Yeasted Tart Dough with Olive Oil
2 tsp active dry yeast
1/2 tsp sugar
1/2 cup warm water
3 tbsp olive oil
1 egg, lightly beaten
3/8 tsp salt
1 3/4 c flour
Dissolve yeast and sugar in warm water in a medium bowl and let stand until bubbly, about 10 min. Add the oil, egg, and salt, then stir in some of the flour. When dough is too sticky to stir, turn out onto a floured surface and kneed until smooth and elastic, about 4 min. Add more flour if necessary to keep from sticking. Set dough in an oiled bowl and cover with towel or plastic wrap. Let rise until doubled in bulk, 45 min - 1 hr. Turn the dough out, roll into thin circle. Place on greased baking sheet. Fill with filling.