To begin, preheat your oven to 350. Spray a mini muffin pan with non-stick spray.
To a large mixing bowl, add your butter, maple syrup, Greek yogurt and milk and whisk together. Add your vanilla and eggs and whisk in.
To the same bowl, add your flour, baking soda and salt. Stir till you have a thick, smooth donut batter.
Use a small cookie scoop, and scoop the donut batter into each muffin cavity till they're all filled about 3/4 way full. Bake in the oven for 9-12 minutes (or till springy to touch and a toothpick inserted comes out clean). Let them cool.
Add the donut holes to a large mixing bowl. Sprinkle the powdered sugar across the top, and gently stir till the powdered sugar has covered each donut hole. Alternatively, you can add the powdered sugar to a small bowl and roll each donut hole around one at a time.
*I recommend topping with powdered sugar just prior to serving. Or, after a few hours the powdered sugar will soak into the donut holes.
**These are best stored in an airtight container at room temperature for a few days.