Lightly grease a 12" x 9" paper tree pan. Or grease a 9" x 13" pan, line with parchment, and grease the parchment. Parchment isn't absolutely necessary, but it makes it easier to get the bubbly, sugary buns out of the pan once they're baked.
1) Whisk together the flour, baking powder, salt, and sugar.
2) Add 2 cups of the cream all at once, then toss and stir the mixture till the dough comes together. If necessary, add additional cream to make the dough cohesive.
3) Gather the dough in your hands and knead it a few times to make sure there are no dry spots.
4) Place the cinnamon sugar in a small, shallow bowl or pan; or in a plastic zip-top bag.
5) Break off pieces of dough about the size of a ping pong ball, or about 1 1/8 ounces. Dip each piece in melted butter or milk, then roll or shake in the cinnamon-sugar to coat.
6) Place the cinnamon-coated dough balls into the pan of your choice in a single layer; they'll be touching one another and, in the tree pan, they'll be quite crowded (which is perfectly OK).
7) You may bake immediately, if you like, for 45 to 50 minutes in a preheated 350°F oven. Or cover the pan with plastic, and place in the freezer overnight, or for up to a week or so. If freezing longer than overnight, and using a paper tree pan, wrap the entire pan in plastic wrap, then in foil.
8) Next day, remove the pan from the freezer, and let the buns rest at room temperature while you preheat your oven to 350°F. The buns don't need to thaw. If you're using a paper tree pan, set it on a baking sheet lined with parchment or foil, to catch any potential drips.
9) If you're baking the buns immediately (not frozen), bake them for 45 to 50 minutes, till the buns in the center are cooked through. You can asses this by taking a toothpick and actually digging into the center bun to take a look; it should look totally baked, not doughy. If the buns have been frozen, bake them for 65 to 70 minutes, testing for doneness as instructed above. Tent them with aluminum foil after 45 minutes of baking.
10) Remove from the oven, and serve immediately, right from the tree pan. If you've baked in a 9" x 13" pan, turn the buns out of the pan onto a serving platter.
11) Dust with confectioners' sugar, if desired, right before serving.