First, make the crust. In a food processor, pulse together flour, sugar and salt to combine. Then add butter and pulse until butter is pea sized. Slowly add the vinegar and then water a little at a time (you may not need it all or you may need more) and pulse until the dough just comes together. Don't add too much water!
You can also do this by hand using two forks.
Form the dough into a disk and wrap in plastic wrap and refrigerate for at lease one hour or up to three days. You can also freeze the dough for up to three months. Also, if you can see specks of butter in the dough that's good for a flaky crust too!
When ready to bake the crust, preheat oven to 425 degrees F
Roll the dough out on a lightly floured surface into a 12-inch circle about 1/8 inch thick.
Place the dough in your pie pan and trim off the extra dough. Form it into letters if you like! I did OY! You can also make your pie edge decorative too. I just pressed a fork into it around the edge.
Put a piece of foil in the crust and fill with dried beans or sugar. Wash just the crust edge with egg wash.
I placed the OY! pieces on a small piece of parchment paper on a baking sheet with the pie. Bake for 10 minutes, remove the OY and bake crust for 5 more minutes for 15 minutes total. While the pie is baking make the filling. Whisk together pumpkin, tahini, eggs and sugar, and the add the hawaij, salt and half and half and whisk until combined. It should be runny.
When the crust is done, lower the oven temperature to 350 degrees and remove the pie weights or beans and foil from the crust. Add the filling, brush the crust edge with egg wash again.
Bake for 45 minutes or until the edges are set but the middle jiggles a bit. If the crust edge starts to brown too much, cover with foil.
While the pie is baking, make the whipped cream. Beat the cream with a hand mixer until it starts to thicken (you can do this by hand with a whisk if you want to also!) Then add the hawaij and powdered sugar and beat until still peaks form.
Cool pie on a cooling rack for at least 3 hours to let pie set.
Garnish with the OY letters and sesame seeds and serve with hawaij whipped cream!
Store leftovers covered in the refrigerator for up to 5 days.