Preheat the oven to 375 F, and position a rack in the center of the oven. Thoroughly spray your donut pans with non stick baking spray.
In a bowl, whisk together the maple syrup, brown sugar, egg, sour cream, milk, melted butter, vanilla and maple extracts, until well combined.
Separately, sift together the flour, baking powder, salt and cardamom.
Add the dry ingredients to the wet, and whisk just until combined.
To easily fill the doughnut pans, spoon the batter into a piping bag, snip off the end, and pipe the batter into the pans, filling them no more than half full.Note: the batter thickens a little as it sits, and can be difficult to use a spoon to spread it into the pans. Piping it in is much quicker and easier. Bake the doughnuts until risen and the tops spring back when gently touched. This will take about 8 minutes using the doughnut pan featured, which is a little smaller than a standard size. With a mini doughnut pan, the donuts may need just 6-8 minutes to bake. With a standard sized doughnut pan, they'll need about 10-12 minutes to bake.
Cool the donuts in the pan for 2 minutes, then gently turn the pan over onto a cooling rack, letting the donuts fall out onto the rack. Spray the pan again with non stick baking spray, refill with the remaining batter, and bake the rest of the donuts. Cool the donuts completely before dipping in the glaze.
Note: if you don't want to make the glaze, simply dip the cooled donuts in granulated sugar until covered in sugar.