Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a mixing bowl, combine the whole wheat flour, all-purpose flour, brown sugar, baking soda, and salt.
Add the cold, cubed butter to the dry ingredients and mix until the mixture resembles coarse crumbs.
Stir in the honey, milk, and vanilla extract until the dough comes together.
Roll out the dough on a lightly floured surface to about ⅛ inch thickness.
Cut the dough into rectangles and place them on the prepared baking sheet.
Bake for 12-15 minutes or until the edges are golden brown.
Let the graham crackers cool on a wire rack before serving.