Combine the flour, brown sugar, baking soda, and salt in the bowl of a food processor fitted with the steel blade. Pulse or mix on low to incorporate. Add the butter and pulse on and off on and off, or mix on low, until the mixture is the consistency of a coarse meal.
In a small bowl, whisk together the honey, milk, and vanilla extract. Add to the flour mixture and pulse on and off a few times or mix on low until the dough barely comes together. It will be very soft and sticky. Lay out a large piece of plastic wrap and dust it lightly with flour, then turn the dough out onto it and pat it into a rectangle about 1-inch thick. Wrap it, then chill it until firm, about 2 hours or overnight.
Sift an even layer of flour onto the work surface and roll the dough into a long rectangle about 1/8 inch thick. The dough will be sticky, so flour as necessary. Using a 3-inch scalloped (or not scalloped) biscuit cutter, cut out as many cookies as you can. Reroll the scraps and cut out more. Using a toothpick or skewer (I like to use the blunt end of a wooden skewer for more dramatic dots), prick the dough to form two dotted rows about 1/2 inch for each side of the dividing line. Place the crackers on one or two parchment-lined baking sheets. Chill until firm, about 15 to 20 minutes in the fridge.
Preheat the oven to 350 degrees F. Bake for 15 to 25 minutes, until browned and slightly firm to the touch, rotating the sheets halfway through to ensure even baking. Cool the cookies on a cooling rack until room temperature.
Meanwhile, make the marshmallow glaze. In a large metal bowl, whisk together 2 tablespoons water, sugar, egg white, cream of tartar, salt and key lime juice. Set bowl over pan of barely simmering water and mix with handheld electric mixer at low speed. Gradually increase speed to high, beating until mixture thickens and becomes a very smooth glaze, about 3-4 minutes. Spread about a teaspoon on each cookie. Using a kitchen torch, torch the tops of each cookie and top with a liberal sprinkling of key lime zest. Note: These get a little funny if they sit out for too long in the heat (hello summer!). If you'd like to make them ahead of time, I recommend making the cookies and then proceeding with the marshmallow glaze just before serving them.