Preheat the oven to 350 degrees.
Separate the pie shells and chill while making the filling. Season the apples with sugar, depending on the level of sweetness in your apples. (Taste the apples. If they are tart, add as much as ½ cup. If you think they are sweet, limit it to ¼ cup sugar.) Add the flour, nutmeg, bourbon, cinnamon, and salt. The mixture should be wet but not soupy.
Line muffin tins with each pie portion. (They won't be perfect. If you'd like to make them more circular, use a rolling pin and shape, but this is not necessary as they will overhang the tin.) Add the apple mixture and crinkle the remaining pie shell around. Add 1 tablespoon of butter on top of each muffin.
Bake until golden brown, about 15-17 minutes. Serve.