Place butter butter cubes on a flour dusted surface. Turn pieces in the flour to coat them.

Place floured butter cubes into a mixing bowl. Add brown sugar, salt and 1 1/3 cups flour. Blend to mix - But do not over blend. Cover with plastic wrap and place in refrigerator.

Preheat the oven to 325°F.

In a mixing bowl, place apple slices, sugar, lemon juice, cinnamon and vanilla extract. Gently toss to mix. Set aside at room temperature until the apples begin to give off their juices, about 10 minutes.

Transfer apple mixture to a 2-quart glass baking dish. Spread it out well, making sure to fill in the corners and spaces and leave a slight depression in the center of the dish.

Remove the topping mixture from the refrigerator.

Sprinkle over the apples mixture, squeezing some of the topping into 1/2 - 1-inch clumps.

Place the baking dish directly on the oven rack.

Bake until the apples begin to turn a rosy color and the juices thicken, about 2 hours. Rotate the dish 2 or 3 times while baking to insure that the topping browns evenly and does not burn. If it does start to burn or brown too quickly, drape dish loosely with aluminum foil.)

When Apple Crisp is done, leave it at room temperature until it cools enough to cut into individual servings, about 20 minutes.

Cut the crisp and serve with ice cream.