Taken from What’s Cooking America:
Pennsylvania Dutch cooking is indigenous to those areas of southeastern Pennsylvania that were settled by the Mennonites and Amish. William Penn (1644-1718), founder of Pennsylvania, was seeking colonists for the Pennsylvania area. The Amish and Mennonites both settled in Pennsylvania as part of William Penn's "holy experiment" of religious tolerance. He wanted to establish a society that was godly, virtuous and exemplary for all of humanity. Encouraged by William Penn’s open invitation to persecuted religious groups, various sects of Christian Anabaptists-Mennonites and offshoots such as the Amish and the Brethren-emigrated from Germany and Switzerland. The first sizeable group arrived in America around 1730 and settled near Lancaster County, Pennsylvania.
These settlers were addicted to pies of all types and they ate them at any time of day. The most famous of their pies is the shoo-fly pie. As the very earliest settlers came to North America by boat, they brought with them the staples of their diet - long-lasting nonperishable that would survive a long boat trip. These staples were flour, brown sugar, molasses, lard, salt, and spices. Arriving in the new land during late fall, they had to live pretty much on what they had brought with them until the next growing season. The women, being master of the art of "making do," concocted a pie from the limited selection that could be found in the larder. This resourcefulness led to the creation of shoo-fly pie.
Visit the Lancaster area of Pennsylvania and indulge in a Pennsylvania Dutch original, the Shoo-fly Pie. First time visitors to the area always comment on this pie and its strange name. Most of the area restaurants and bakeries sell this favorite pie. The pie is more like a coffee cake, with a gooey molasses bottom. Some cooks put chocolate icing on top for a chocolate shoo-fly pie. Some use spices; some don't. The bottom of the pie can be thick or barely visible and is referred to as either a "wet bottom" or a "dry bottom." Everyone agrees the shoo-fly pie is best when slightly warmed and with whipped cream on top.
The origin of the name has been debated for years and will probably never ultimately be solved. The most logical explanation is related to the fact that during the early years of our country, all baking was done in big outdoor ovens. The fact that pools of sweet, sticky molasses sometimes formed on the surface of the pie while it was cooling; invariably attracting flies, show how such a pie could come to be called shoo-fly pie.
I cup flour
1/2 cup dark brown sugar
1/4 cup (1/2 stick) plus 1 tbsp butter
1/2 cup molasses
1/2 tsp baking soda
2/3 cup hot boiling water
9” diameter unbaked pie crust
1. Pre-heat oven to 325 degree F. Combined flour and brown sugar in a medium bowl. Mix well.
2. For the topping, transfer ½ cup of the flour mixture to a separate bowl and mix in the 1 tbsp of butter with your fingers until crumbly. Set it aside.
3. Melt the ¼ cup butter and let it cool slightly. Beat eggs with a whisk until blended. Stir in the molasses and melted butter. Gradually stir in the flour mixture until well mix.
4. Stir in the baking soda. Gradually stir in boiling water until well mix.
5. Pour the mixture into the pie crust. Sprinkle the reserved topping and bake it for 50 minutes or until the filling is puffy and set.
6. Remove from oven and let it cool down for 15-20 minutes before serving.