Place a rack in the upper third of the oven and preheat oven to 350 degrees F. Lightly grease a doughnut pan and set aside.
In a medium bowl, whisk together flour, baking powder, baking soda, salt, cinnamon, and sugar. Set aside.
In a small saucepan over medium-low heat, melt butter. Butter will begin to crackle and pop as it melts. Once the water has evaporated the butter will quiet down and begin to brown. Keep an eye on it, it browns quickly. The butter will begin to smell nutty. Remove from heat and immediately and set aside to cool.
In a small bowl whisk together egg, milk stout, and vanilla extract. Add browned butter and whisk into the wet ingredients.
Add the wet ingredients all at once to the dry ingredients. Stir together until no flour bits remain and all of the ingredients are well combined being sure not to overmix batter.
Transfer batter into a plastic sandwich bag. Snip the tip with a pair of scissors and pipe batter into each doughnut mold about three-quarters full with batter.
Place in the oven and bake for 8 to 10 minutes. Keep an eye on them and try not to over-bake them. Remove from the oven and allow to cool in the pan before inverting onto a wire rack to cool completely.
While the doughnuts cool, make the glaze.
for the maple bacon glaze
In a medium bowl, mix the confectioner’s sugar with maple syrup and vanilla extract until sugar starts dissolving. Slowly add milk stout to thin out the glaze. You might only need 1 tablespoon so mix as you go. Add more if necessary.
Spoon glaze over each doughnut. While glaze is still wet, add the bacon crumbles on top of each doughnut. Doughnuts are best served the day they’re made. Store in an air-tight container and refrigerate if you have any left after day one (doubtful!).