In the bowl of a heavy-duty mixer, combine the Bin Inn Gluten Free Flour Mix, salt, and sugar. Mix on low to blend.
In a small bowl, dissolve the sugar in the lukewarm water and add the yeast. Let it sit for about 5 minutes, or until the mixture becomes foamy.
Add the yeast mixture to the dry ingredients and mix well.
Add the melted butter, egg whites, and vinegar, and beat on high for 3 minutes until the dough is smooth and elastic.
To form the loaves: Using a wet spoon or your hands, place the dough onto a greased and cornmeal-dusted baking sheet in the shape of long French loaves, or place it into French-bread pans.
If you like, brush the loaves with melted butter for a golden finish, then slash the tops of the loaves diagonally every few inches.
Cover the dough and let it rise in a warm place until doubled in size, about 20-25 minutes.
Preheat your oven to 200°C.
Bake the loaves for 40-45 minutes, or until golden brown and firm to the touch.
Remove the loaves from the oven and allow them to cool on a wire rack. If desired, brush with more melted butter while the bread is still warm.
