In a stand mixer fitted with the paddle attachment, mix together the whole-wheat and cake flours, baking soda, salt, and cinnamon (if using) on low speed. Add the brown sugar, butter, honey, vanilla, and water and mix on medium-low speed until just evenly combined and no flour remains.
Divide the dough into two equal pieces. Form each into a rectangle 9 inch / 1.5cm thick and wrap in plastic. Refrigerate the dough for at least 1 hour or freeze for up to 1 month.
Preheat the oven to 350°F / 175°C.
On a lightly floured silicone mat or piece of parchment paper, roll each piece of the chilled dough into a 10 by 13-inch / 25 by 33cm rectangle, about ⅛ inch / 3mm thick. Transfer the mat or parchment paper onto a baking sheet.
Dock the dough with a fork all over to prevent it from puffing too much. Use a pastry or pizza wheel to score the dough all the way through, cutting the crackers to whatever size you like, so when they are baked and cooled, they easily break into neat graham crackers.
Bake for about 18 minutes, or until the crackers are golden brown and dry. Check early as baking depends on thickness.
Allow to cool completely on the baking sheet. Then break apart and store wrapped in an airtight container in a dry, cool place. If the crackers lose their snap, you can reheat them in a 350°F / 175°C oven for about 5 minutes.
