Be sure all ingredients are at room temperature before starting.
In a heavy mixer bowl, add bread mix and yeast.
In a small bowl, mix milled flax seed and water together and let sit.
In a medium bowl, mix the warm milk, eggs, melted butter and cider vinegar together until blended. Add the milled flax seed mixture to the wet ingredients. Pour all of this into the dry ingredients in mixer bowl and mix on medium speed for 5 minutes. Let sit for 30 minutes in a warm place to rise.
Combine the brown sugar and cinnamon. Set aside.
Preheat oven to 350°F. Place parchment paper on 10x12-inch baking pan and spray with nonstick spray. When bread dough has finished rising, scoop it out onto the sprayed parchment paper and spread out dough evenly.
Spread softened butter onto dough and top with sugar and cinnamon mixture.
Take a dull knife and marble/swirl through dough both length and width like you were cutting it. This will swirl the cinnamon mixture throughout the dough and will also put divets for the pull apart effect. Bake for 30 minutes.
Prepare the glaze in a small bowl by whisking the powdered sugar, 2 Tbsp. milk and vanilla until smooth. Drizzle glaze evenly over warm pull aparts. Best when served warm.
Shortcut Note* Use the dough cycle on your bread machine to mix and rise the dough. Form dough and bake as directed in recipe.