In a medium bowl whisk flour, semolina, yeast and salt until combined.
Cut butter into the flour mixture with a fork. Next, mix in the egg.
Add water, 1 Tbsp at a time, until dough just comes together when pressed in your hands.
Turn out shaggy dough onto the counter and knead until a dough forms, about 2-3 minutes.
Cover with plastic and let rest at least 2 hours in the fridge.
Preheat oven to 300ºF.
Roll out dough using a pasta roller or by hand with a rolling pin. (lightly dust surface with semolina if rolling out on the counter) You want to roll the cracker out as thin as you can.
Line a sheet tray with parchment, and grease lightly with olive oil.
Lay out cracker sheets on the oiled tray and spray with water. Top with lots of sesame seeds, pepper and just a touch of flake salt. Prick all over with a fork.
Place another sheet of parchment on top of the crackers and top with another baking sheet.
Bake for 20 minutes with the crackers covered. Remove top sheet tray and bake for an additional 10-20 minutes until crackers are crisp and golden.