Start by combining the yeast and 1 Tbsp brown sugar in the bowl of an electric mixer and then slowly pouring in the warm water, while stirring everything together. Allow 10 minutes for the mixture to sit and the yeast to activate (It'll become foamy when done right!).
Meanwhile, melt the butter and milk together over the stove top on low to medium heat, stirring frequently until the butter has fully melted. NOTE: You don't want the mixture to get too hot or boil! Set aside and let it cool until WARM.
Add lukewarm butter-milk mixture to yeast and mix until well combined. Add eggs, one at a time and continue mixing on low speed until well combined. Add in molasses and mix until well combined.
Next, combine the all-purpose flour, bread flour, brown sugar, sea salt and spices to the wet ingredients and mix on low-speed until well combined.
Change “mixer head” to kneading accessory and knead dough for 5-10 minutes on medium-high speed until dough ball becomes smooth and elastic and dough springs back when lightly pressed with 2 fingers. NOTE: If dough is too sticky, add 1 Tbsp of flour at a time until texture is achieved!
Once dough ball is perfectly kneaded, add it to a lightly greased bowl and cover with plastic wrap. Let it sit and rise for 1 hour to an hour + 15 minutes.
In the meantime, you can work on the filling!