In a saucepan, warm the milk as you consistently whisk. Be careful not to heat until hot. Remove from heat and pour into your mixing bowl. Add the yeast packets and let sit for 5 minutes. Add brown sugar, butter, salt, gelatin, apple cider vinegar, eggs and flour. Combine using a hook attachment on your Kitchenaid making sure to scrape down sides as needed with a rubber spatula. Add up to 1/4 C more gluten-free all-purpose flour as needed to have the dough come together. Cover and let rise at room temperature 60 minutes. Preheat oven to 400° and line two baking sheets with silicone mats. In a large bowl, combine the water and baking soda. With lightly (gluten-free) floured hands, turn out your dough and break into two, continue breaking those pieces down until you have 12 balls of dough. Roll each out into a long rope then shape into a pretzel. Dip each pretzel into the baking soda and water bath until fully submerged then place on the mat. Bake at 400° for 12-15 minutes or until golden brown. Remove and brush with softened butter and sprinkle with coarse salt.