In a bowl, whisk together flour, milk, eggs, sugar and salt until no lumps remain. Let stand for 30 minutes. (You can mix batter the night before, cover and refrigerate. Remove from refrigerator when you begin preheating oven.)
Preheat oven to 450°F. While oven preheats, place a large slope-sided baking pan or ovenproof skillet into oven and add butter. When butter is melted, remove from oven.
Pour pancake mixture into heated pan and return to oven. Bake pancake for 15 to 20 minutes, until edges are puffed high and golden.
While pancake bakes, in medium skillet, sauté apples in butter until tender, 5 to 10 minutes. Add brown sugar and stir until dissolved. Transfer to serving bowl.
To serve pancake, be sure guests are at the table when you bring it in, as it will slump quickly. Cut pancake into quarters, and fill each serving with sautéed apples. Pass the whipped cream on the side, if desired.