Granny Smith apples are the key to this crisp, because their tartness is delicious with the sweet, crunchy oat-flecked crumb topping. Slideshow: Fruit Cobblers and Crisps
Preheat the oven to 350°. In a large bowl, toss the apples with the lemon juice and granulated sugar. In a very large skillet, melt the 2 tablespoons of butter. Add the apples and cook over moderate heat, stirring occasionally, until softened but not browned, about 5 minutes. Scrape the apples into a large baking dish.
Wipe out the bowl. Add the flour, brown sugar, oats, cinnamon, salt, cardamom and the 1 stick of diced butter and, using your fingers, rub the butter into the dry ingredients until the mixture resembles coarse meal. Press the topping into clumps and scatter it over the apples.
Bake the crisp for 45 to 50 minutes, until the apples are bubbling and the topping is golden. Let cool, then serve warm with crème fraîche or ice cream.
The apple crisp can be made earlier in the day and reheated.