1) Preheat the oven to 350°F. Grease the wells of two standard doughnut pans. If you don't have two pans, no problem; you can bake in two shifts. Don't have a doughnut pan? See "tips," below.
2) In a medium-sized mixing bowl, beat together the butter, vegetable oil, and sugars till smooth.
3) Add the eggs, beating to combine.
4) Stir in the baking powder, baking soda, salt, and vanilla or maple flavor.
5) Stir the flour into the butter mixture alternately with the milk, beginning and ending with the flour and making sure everything is thoroughly combined.
6) Distribute the bacon pieces evenly among the wells. Drizzle the maple syrup over the bacon, using about 3/4 to 1 teaspoon per doughnut.
7) Spoon the batter evenly into the pan(s), filling the wells up to the rim.
8) Bake the doughnuts for 15 minutes, or until they're raised and firm, and a toothpick inserted into the middle of one comes out clean.
9) Remove them from the oven, and place on a rack or trivet. Loosen the edges of the doughnuts with a table knife or spatula, and immediately turn the pan(s) over onto a piece of parchment or waxed paper. Rap the edges of the pan gently to loosen the doughnuts, and lift it off.
10) Place the doughnuts on a rack to cool slightly while you make the glaze.
11) To make the glaze: Stir together the confectioners' sugar, salt, and enough maple syrup to make a spreadable glaze.
12) Spread the glaze over the doughnuts. Serve warm, or at room temperature. Wrap any leftovers loosely in plastic, and store for 1 day at room temperature; refrigerate or freeze for longer storage.
Yield: 12 doughnuts.