Preheat oven to 350°F
Thoroughly grease donut pan (if not non-stick) with either butter or cooking spray
In a medium to large bowl, mix together flour, dark brown sugar, sugar, baking powder, baking soda, cinnamon, nutmeg, and salt. Whisk together to make sure all ingredients are combined.
In a small bowl, add egg, vanilla, buttermilk, melted butter and oil. Whisk together until combined.
Pour wet ingredients into dry and mix until just combined.
Spoon batter into donut pans. Cavities should be about 2/3 full.
Bake donuts for about 18 minutes. You can test one with a toothpick to make sure it comes out clean.
While donuts are cooking, melt your butter and whisk in brown sugar until it is incorporated into the butter. Then add maple extract, heavy cream and powdered sugar, whisking into a glaze. The glaze will be a little thick but when you take spoon or whisk out of it, it should flow freely off the utensil back into the bowl. If it does not, add more cream ½ tbsp at a time. Make sure the bowl you do this in is wide enough to dip and hold a donut in.
Remove donuts from pan onto wire rack. The side that was the bottoms while cooking is often more attractive and uniform for glazing so it's often easiest to put wire rack upside down on top of donut pan and flip both over to remove all with the side you'd like facing up.
Once donuts are completely cool, after about 30-60 minutes. Dip the tops into the glaze and then returning them to the wire rack. Once glaze has set you can dust a little extra powdered sugar on the tops.
