3 cups (13.5 ounces or 375 grams) unbleached all-purpose flour
1 cup (176 grams) dark brown sugar, lightly packed
1/2 teaspoon (3 grams) baking soda
3/4 teaspoon kosher or coarse sea salt (4 grams)
7 tablespoons (3 1/2 ounces or 100 grams) margarine, cut into 1-inch cubes and frozen (if using salted margarine decrease salt slightly)
1/3 cup (114 grams) mild-flavored honey, such as clover
5 tablespoons (77 grams) almond or soymilk
2 tablespoons (27 grams) pure vanilla extract
12 tablespoons marshmallow fluff
2-3 ounces finely chopped chocolate
Combine the flour, brown sugar, baking soda, and salt in the bowl of a food processor fitted with the steel blade or in the bowl of an electric mixer fitted with the paddle attachment. Pulse or mix on low to incorporate. Add the margarine 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. Chill it until firm, about 2 hours or overnight.
Preheat the oven to 350. Remove half of the dough from the refrigerator and roll it out between two pieces of parchment paper. Cut out circles using a round cookie cutter or the top of a drinking glass and transfer the circles to a parchment lined cookie sheet. (If the dough gets too sticky while working with it place the parchment with the dough on a cookie sheet in the freezer for a few minutes) Fill four of the circles with a small amount of marshmallow fluff (less than a teaspoon) and sprinkle with a small amount of chocolate. Marshmallow fluff is very sticky so the easiest way to push it off the spoon onto the hamentashen is with a slightly wet finger. Use significantly less filling than might seem right because marshmallow fluff expands in the oven. For 2 1/2 inch circles use a scant teaspoon fluff. Fold up two sides of the circle and pinch them together. Lift the third side and pinch the remaining two corners closed. Repeat with the remaining circles. (It is important to fill no more than four hamentashen at a time because marshmallow fluff begins to ooze as soon as it is spooned out onto the dough an the hamentashen need to be folded before the filling has oozed too much). Roll out and fill the remaining dough.
Bake the hamentashen for 8-10 minutes, or until set. Transfer to a cooling rack and let cool completely before enjoying.