Preheat oven to 350°F (177°C). Spray donut pan with non-stick spray. Set aside.
Whisk the flour, baking powder, baking soda, cinnamon, nutmeg, cloves, and salt together in a large bowl. Set aside. Whisk the melted butter, egg, brown sugar, milk, yogurt, and vanilla together until completely combined. Pour the wet ingredients into the dry ingredients and whisk until just combined. Do not overmix. The batter will be thick.
Spoon the batter into the donut cavities I highly recommend using a large zipped-top bag for ease. Cut a corner off the bottom of the bag and pipe the batter into each donut cup, filling about halfway. (If you only have 1 donut pan that bakes less than 8 donuts, keep the remaining batter in the bowl at room temperature until you can bake the next batch.)
Bake for 10-11 minutes or until the edges and tops are lightly browned. Gently poke a donut with your finger. If it bounces back, the donuts are done. Allow donuts to cool for a few minutes in the pan, then transfer to a wire rack set on a large piece of parchment paper. Bake the remaining donut batter and once baked, transfer to the wire rack.
In a small saucepan over low heat, melt the butter and maple syrup together, whisking occasionally. Once the butter has melted, remove from heat and whisk in the sifted confectioners’ sugar and maple extract. Taste. Add a pinch of salt if desired.
Cool for 2-3 minutes, then dip each donut into the icing. The icing quickly thickens, so feel free to place it back over heat as you dip. Place dipped donuts back onto cooling rack as excess icing drips down. Feel free to double dip them (I usually do!).
Donuts are best served immediately. Leftovers keep well covered tightly at room temperature or in the refrigerator for 2 days.
