In a large bowl, mix flour and salt together for the pie crust.
With a standing mixer or pastry cutter, work the butter into the flour until it resembles coarse crumbs.
Gradually add ice water to the flour mixture, 1 Tbsp at a time, until the dough comes together.
Form the dough into a ball, wrap it in plastic wrap, and refrigerate for at least 30 minutes.
Preheat the oven to 375°F (190°C) and prepare a 9" or 10" pie dish.
On a floured surface, roll out the pie dough to about 1/4" thick and transfer it to the pie dish.
Trim off any excess dough, leaving a slight overhang. Tuck the ends under and crimp the edges. Set aside.
In a large bowl, combine pumpkin puree, apple butter, brown sugar, and spices for the filling.
Add eggs and half & half to the filling mixture, mixing until smooth.
Pour the filling into the prepared pie crust, spreading it evenly.
In a small bowl, mix together brown sugar, flour, and chopped pecans for the streusel.
Cut in cold butter until the streusel mixture resembles coarse crumbs.
Sprinkle the streusel over the pie filling.
Bake the pie for 30 minutes.
After 30 minutes, carefully sprinkle the streusel over the pie.
Return the pie to the oven and bake for an additional 30-35 minutes, or until set.
Allow the pie to cool for at least 30 minutes before serving.
Serve with whipped cream and refrigerate any leftovers.