Separate ½ cup of flour and set aside. In a large bowl, stir together the remaining flour, the sugar, salt and yeast together until evenly dispersed. Set aside.

In a heatproof bowl, heat the water, half-and-half and butter together in the microwave until the butter is melted and the mixture is hot to touch. Stir to combine, then slowly pour the butter mixture into the flour mixture. Add the egg, vanilla (if using) and only enough of the reserved ½ cup flour to make a soft dough. (I only needed ¼ cup.) Dough will be ready when it has an elastic, stretchy consistency and it gently pulls away from the side of the bowl.

On a lightly floured surface, knead the dough for about 3 to 4 minutes. Toward the end, place the dough in a bowl and gently work in 1/2 cup of the sprinkles.

Grease a bowl with non-stick spray and place the dough in the bowl. Allow to rest for about 10 minutes. Meanwhile, preheat the oven to 200°F.

After 10 minutes, use a lightly floured rolling pin to roll the dough into a 14 x 8-inch rectangle.

In a clean bowl, mix together the vanilla sugar (or granulated sugar) and cinnamon.

Spread melted butter over top of the dough. Sprinkle evenly with cinnamon sugar mixture. Tightly roll up the dough. (Cinnamon may spill out the edges.) Cut the roll into 12 even pieces and place in a lightly greased 9-inch round pan.

Turn off the oven. Loosely cover the rolls with a sheet of aluminum foil. Allow them to rise in the warm oven for 60-90 minutes or overnight, up to 8 hours.

After the rolls have doubled in size, preheat the oven to 375°F. Bake for 25 to 30 minutes, until lightly browned. Covered with aluminum foil after 15 minutes to avoid heavy browning.

While the rolls are cooking, make the glaze. In a large clean bowl, add the confectioner's sugar. Add melted butter, vanilla and 2 tablespoons milk and stir until smooth. (If glaze is too thick, add more milk. If it is too runny, stir in a teaspoon of confectioner's sugar.)

Use immediately to top cinnamon rolls with glaze.