In a medium bowl, whisk the whole wheat flour, all-purpose flour, baking soda, salt, and cinnamon together. Set aside.

In a large bowl using a handheld or a stand mixer fitted with a paddle attachment, beat the butter and brown sugar together on medium-high speed until the mixture is light and creamy, about 3 minutes. Add the honey, molasses, and vanilla and beat on medium-high speed until combined. Scrape down the sides and bottom of the bowl and beat again as needed to combine.

Add the milk and the dry ingredients to the wet ingredients and mix on low speed until combined. The dough should be soft.

Divide the dough in half and shape each portion into a flattened square. Wrap each square tightly in plastic wrap and refrigerate for at least 1 hour and up to 2 days.

If the dough has chilled for longer than 1 hour, let it sit at room temperature for about 20 minutes before rolling so it can soften slightly. Working with 1 portion of dough at a time, place a silicone baking mat on your work surface (to keep the parchment from sliding around), then place a lightly floured sheet of parchment paper on top. Place the dough on the parchment, lightly flour the top of the dough, and cover with a second sheet of parchment. Roll into a rectangle that’s evenly 1/8-inch thick.

Remove the top sheet of parchment. Trim the edges if desired, then use a pizza cutter or sharp knife to cut the dough into evenly sized rectangles or squares. Cut all the way through the dough, but don’t separate the pieces—leave them together as one slab. Use a fork to dock each cracker several times. Transfer the parchment with the cut dough onto a baking sheet. Repeat steps 5 and 6 with the second square of dough.

Refrigerate both baking sheets (or stack the slabs of dough on top of each other, separated by parchment) for 20 minutes while you preheat the oven. Chilling helps prevent spreading; the crackers should spread very little in the oven.

Preheat the oven to 350°F (177°C).

Bake for about 16 minutes, rotating the pan(s) halfway through. The crackers are done when they are lightly browned around the edges and appear dry on top.

Allow the crackers to cool on the baking sheet for 5–10 minutes before transferring to a cooling rack to cool completely. They will continue to crisp considerably as they cool.

Once completely cool, use a sharp knife to cut along the seams to separate the graham crackers. Store cooled graham crackers in an airtight container at room temperature for up to 1 week.