To make the caramel sauce. Pour water into a medium sauce pan. Pour your sugar into the center of the pan. Be careful not to let the sugar crystals touch the side of the pan. Cover and bring to a boil over high heat. Uncover and continue to boil until the syrup is thick and straw colored and your thermometer registers 300oFdegrees, about 15 minutes. Reduce your heat to medium and continue to cook until the sugar is deep amber and registers 350oF degrees, about 5 minutes.Meanwhile, bring your heavy cream to a simmer in a saucepan over high heat. If you cream begins to simmer before your sugar is ready, remove the cream from heat and set aside. Remove the sugar syrup from heat. Carefully pour about 1/4 of your cream into your sugar syrup. The mixture will bubble vigorously. Let the bubbling subside, and add in the remaining cream. Whisk gently until smooth, then whisk in your butter and your salt
To make the streusel topping: In a medium sized mixing bowl combine the brown sugar, oats, flour, and cut in the softened butter (you can use a pastry cutter to do this or two knives). Set aside.
To prepare the crust: Preheat oven to 350oF degrees. Prepare a 13x9 pan with foil being sure to leave the edges hanging over for easy removal. In a small bowl combine the sugar, flour, and salt. Add in the melted butter. Stir to combine. Press into pan and bake for 20 minutes.
To make the apple filling: While the crust is baking, dice the apples and place in a medium bowl. Toss with the flour, sugar and spices. Spread the apples over the par-baked crust. Drizzle with a 1/2 cup of caramel sauce.
Crumble the streusel topping over the apples and caramel sauce. Bake for 30 minutes at 350oF/180oC
Drizzle with more caramel sauce before serving. Cut into 16 small squares or 12 generous sized squares.