If you've never tried shoofly pie, prepare to have your mind blown by this classic Pennsylvania tradition. Perfect for holiday dessert, it's a molasses pie or cake created by the Pennsylvania Dutch in the 1880s that is comforting, flaky, and delicious. Shoofly pie is a tradition hailing from the state's Amish community, and it likely got its name from the flies that were attracted to it because it's so sweet. You probably already have all the ingredients for this in your kitchen, except maybe the molasses (a quick run to the grocery store should fix that). And preparation is easy and to-the-point: simply mix the filling in one bowl and the topping in another, fill your pie crust, and watch it bake to perfection. Use your favorite pie dough recipe, or use a store-bought deep-dish pie crust if you're in a pinch. Great for holiday gatherings — or for yourself — with strong black coffee for breakfast, as is tradition.
Preheat the oven to 425°F.
On a floured surface, roll the dough to fit a nine-inch deep-dish pie plate. Trim and flute the edges. Refrigerate for at least 30 minutes.
Meanwhile, make the filling. Mix the brown sugar, molasses, egg, flour, and baking soda. Gradually stir in the boiling water. Let it cool completely.
Line the unpricked crust with a double thickness of foil. Fill it with pie weights, such as dried beans or uncooked rice. Bake on a lower oven rack for 15 minutes. Remove the foil and pie weights, then brush the crust with egg yolk. Bake five minutes. Cool it on a wire rack.
Reduce the oven setting to 350°F.
In another bowl, whisk together the first four topping ingredients. Cut in the butter until crumbly. Add the filling to the crust, then sprinkle it with topping. Cover the edges of the pie with foil.
Bake until the filling is set and golden brown, 45-50 minutes. Cool it on a wire rack.
Store it in the refrigerator.