Preheat the oven to 350 degrees.
Combine Wet Ingredients – In a measuring cup, combine buttermilk, eggs and vanilla extract.
Combine Dry Ingredients – Add flour, salt, cardamom and baking powder in a bowl.
Beat Butter and Sugar – In a mixing bowl with the paddle attachment, cream the butter and sugars until combined.
Alternate Dry & Wet Ingredients – With the mixer on low, slowly alternate the wet ingredients with the dry until the ingredients are mixed. Scrape down the sides and bottom of the bowl.
Fold in mashed bananas.
Fill a piping bag and pipe into the donut pan.
Bake for 12-15 minutes or until golden brown.
To make the glaze, whisk all of the ingredients for the glaze in a medium bowl.
Add more milk if you need to adjust the texture.
Once the donuts are baked, let them cool and then remove them onto a cooling rack.
Add parchment paper under the cooling rack, then drizzle the glaze over the donuts.