In a large microwave-safe bowl, combine squash and water. Cover and cook on high for 5 minutes or until crisp-tender. Drain; transfer to a large resealable plastic bag. Add the oil, thyme, parsley, salt and pepper; seal bag and shake to coat. Set aside. In a small bowl, combine the flour, pecans, sugar, nutmeg and cinnamon; set aside.
Unfold pastry sheets on a lightly floured surface. Roll each pastry to 1/8-in. thickness; transfer each to an ungreased baking sheet. Sprinkle with pecan mixture. Arrange squash slices to within 1-1/2 in. of edges, alternating slices of butternut and acorn squash.
Fold up edges of pastry over filling, leaving centers uncovered. Brush pastry with egg. Dot squash with butter. Bake at 375° for 35-40 minutes or until golden brown. Yield: 2 tarts (8 servings each).