7 oz/200 g graham crackers and saltines (any combo you like. I used about 2 parts saltines to 1 part graham crackers)
1/2-3/4 cup soft unsalted butter
2 Tbsp. granulated sugar
Preheat oven to 350 F (180 C), with the oven rack in the middle position.
Crush the graham and saltine crackers into fine crumbs by placing them in a plastic bag and bashing them with a rolling pin until they're a coarse powder (you could also do this in the food processor, but it's much more fun by hand). Add the sugar and mix (or pulse) to combine. Pour the sweetened crumbs into a medium bowl. Add the soft butter a little at a time until it sticks together almost like a dough (you want it to be quite moist). Put the crust mixture into a 9" (22 cm) pie pan. Using your hands and a measuring cup, press the crumbs into the bottom and sides of the pan. Make sure it's well packed.
Place the pie crust in the oven and bake for 18-20 minutes, or until golden brown. Allow to cool slightly before adding the filling (it doesn't need to be completely cold). Don't turn the oven off, you'll need it again.
NOTE: The ratio of saltines to graham crackers is up to you. However, the proportions you use will affect how to garnish the pie. If you use all or mostly graham crackers, a sprinkling of coarse salt on top of the whipped cream balances the sweetness. But if you use all/mostly saltines, the salt will be too much.
Also, the amount of butter you use will change with the humidity. Keep adding it until the crumbs clump together in large pieces. I found that to be almost the full 3/4 cup.