The name for this Pennsylvania Dutch treat likely came from the flies it attracts when it's pulled from the oven and left to cool on a breezy windowsill.
1/2 (14.1-ounce) package refrigerated pie dough
3.4 ounces all-purpose flour (about 3/4 cup)
1/2 cup packed dark brown sugar
1 tablespoon unsalted butter, cut into pieces
1/4 teaspoon salt
1 large egg
1 teaspoon vanilla extract
1 cup molasses
3/4 teaspoon baking soda
3/4 cup boiling water
How to Make It
Preheat oven to 350°.
Fit dough into a 9-inch pie plate. Fold edges under; flute.
Weigh or lightly spoon flour into dry measuring cups; level with a knife. Place flour and next 3 ingredients (through salt) in a food processor; process until a sandy texture. Remove and set aside 1/2 cup flour mixture from food processor, reserving remaining mixture in food processor bowl.
Combine egg and vanilla in a medium bowl, stirring with a whisk. Gradually add molasses, stirring with a whisk. Stir baking soda into 3/4 cup boiling water. Add baking soda mixture to molasses mixture, whisking until blended. Stir in flour mixture from food processor bowl, stirring with a whisk until smooth. Pour mixture into prepared crust. Sprinkle with reserved 1/2 cup flour mixture.
Bake at 350° for 37 minutes or until slightly puffed and surface begins to crack. Cool completely on a wire rack. Serve at room temperature.