For Brioche Dough:
-2 1/2 cups unbleached all-purpose flour
-1 1/2 teaspoons instant yeast
-1/4 cup cool water (about 70 degrees F)
-4 large eggs
-2 tablespoons sugar
-3/4 teaspoon sea salt
-1 cup (8 ounces) cold unsalted butter
For Maple Frosting:
-3 ounces unsalted butter
-1/2 teaspoon salt
-2 cups powdered sugar
-3/4 cup maple syrup
-1 cup bacon crumbles
Place 1 1/2 cups of the flour, the yeast, water, and whole eggs in a mixer bowl. Beat at medium speed, using the flat beater paddle, until smooth. Cover the mixture and let sit for 45 minutes. It will develop some bubbles, but not change a lot due to the thinness of the batter. However, the yeast is getting a head start.
Add the remaining flour, the sugar, and salt, and beat for 8 to 10 minutes, until the dough cleans the sides of the bowls and is shiny and elastic.
Sprinkle a work surface with a small palmful of flour (about 2 tablespoons of flour). Place the butter on the flour. Pound with the side of a rolling pin until it has become a cohesive rectangle about 1/4-inch thick. Fold it over several times as you pound; it will become pliable without getting too warm or soft. Add it to the dough and beat until it is fully incorporated.
Cover the dough with a towel and let it rise in a warm room for an hour. It should be very soft and have risen about 1/3. Turn the dough out on a lightly floured surface and fold it over several times. (Use a bench knife or dough scraper to scrape up any bits that stick to the table.) Place the dough in a greased bowl, cover the bowl, and refrigerate for at least 4 hours (or up to 16). The dough will firm up considerably and be easier to work with.
Turn the dough out onto a lightly floured work surface. Using a rolling pin with handles, roll it out to a thickness of 1/2 inch. If the dough is difficult to handle after rolling, place it in the freezer for 20 minutes. Cut the dough using a donut cutter or two round cutters of graduated size. Dip the cutters in flour each time to make it easier.
Cover and let rise until double, 30-40 minutes. At 25 minutes, begin to heat vegetable oil in high-sided stock pot to 350 degrees F.
While the donuts are rising, make the maple frosting. Heat butter over low heat until it is melted. Remove from heat. Stir in powdered sugar until smooth. Stir in tablespoons of maple syrup one at a time, until desired consistency. Set aside until ready to frost.
When the oil reaches 350 to 360, carefully place 4 or 5 doughnuts in the oil. Fry for 1 minute, then use a slotted spoon to flip them over carefully. Fry the other sides for 1 minute, then flip the doughnuts again and fry for 30 seconds more, or until dark golden brown. Remove the doughnuts from the oil and drain them on paper for 30 seconds before frosting. Generously spread frosting over the top of the donut and sprinkle with bacon.