Apple Crisp

For the crisp topping:

• 1 cup all-purpose flour
• 2/3 cup packed dark brown sugar
• 3/4 teaspoon ground cinnamon
• 1/8 teaspoon salt
• 8 tablespoons (1 stick) unsalted butter, cut into 1/2-inch pieces and chilled

For the apple filling:

• 2 pounds firm, sweet apples (4 to 5 medium-large apples)
• Up to 1/4 cup water

For serving (optional):

• Vanilla ice cream or heavy cream