Mix the dry ingredients in a large mixing bowl.
Add the cubed butter and crumble it with the flours until it resembles wet sand.
Add the vanilla and milk.
Form into a dough.
Roll the dough into a large rectangle between two pieces of parchment paper (about 3-4 mm thick, 1/8th inch).
Cut off the sides to make the shape more rectangular. Add it to the middle, and roll again.
Cool the sheet of dough in the fridge for 30 minutes.
Preheat the oven to 175°C (347°F).
Trim the rectangle into 16 symmetrical crackers with a sharp knife or pizza cutter, keeping them attached.
Transfer to a baking sheet.
Bake for 8-10 minutes, until golden.
While cooling, use a large knife to separate the crackers.
Leave them in the baking sheet to cool.