In a small saucepan, heat the water, milk and butter until too hot touch. Remove from heat and allow to cool to lukewarm (about 120F).
Meanwhile, in a large bowl or the bowl of a stand mixer fitter with a kneading hook, combine 2 1/2 cups of the flour, the white sugar, salt and the instant yeast. When the milk mixture has cooled enough, add to the flour mixture, along with the egg. Mix until combined. Start adding additional flour in small increments and knead until you have a smooth, moist (but not sticky) dough. Remove dough to a greased bowl, cover with plastic wrap and allow to rise until doubled, about 45 minutes.
Meanwhile, prepare a 10-inch springform pan by lightly greasing, then lining completely with one sheet of parchment paper, The parchment should completely cover the bottom and most of the sides. Set aside.
In a medium bowl, combine the brown sugar, cinnamon and cold butter. Cut the cold butter in to the brown sugar using a pastry cutter or two knives until you have pea-sized crumbs.
Remove 1/2 cup of the brown sugar/butter mixture and scatter it on to the bottom of your parchment lined pan. Drizzle 3 Tbsp of hot tap water over-top and stir to combine in to a bit of a sauce. It will have bits of un-dissolved butter, but don't worry about that. I doesn't need to be smooth. If using cherries and/or nuts, scatter them on top of the bit of sauce. Set aside
When dough has risen, remove to a floured surface and roll in to a 11x16 rectangle. Even scatter the remaining brown sugar/butter mixture over the dough, then, starting with the long edge, roll the dough up jelly-roll style. Trim both ends slightly to even up, then slice the dough log in to 11 equal-width slices. Place each slice, cut side down, in to your prepared pan, on top of the sauce and cherries/nuts, if using.
Preheat oven to 350F.
Cover pan with a clean tea towel and set aside to rise until puffy and almost doubled, about 30 minutes.
Place pan with rolls on top of a baking sheet. Bake in preheated oven for about 40 minutes, or until deep golden and hollow sounding when tapped. You may want to check at the 30 minute mark and if already well browned, cover loosely with a sheet of foil.
Remove from oven and immediately invert on to a piece of parchment paper. Immediately, loosen the side of the springform pan and remove, then remove the parchment paper and discard. Allow to cool completely before eating (to avoid a gummy dough). If you like you can re-warm. Serve with a bit of butter, if you like.