1. Preheat oven to 425°F and lightly grease 2 donut pans. In a large mixing bowl, vigorously whisk the oil, butter, sugar and brown sugar until smooth and slightly frothy. Add the eggs and vanilla, then whisk to combine.
2. Sprinkle baking soda, baking powder, chai spice and salt over the batter then whisk until completely combined.
3. Use a spatula to stir the flour and milk alternately into the batter, beginning and ending with the flour. The batter will be fairly thick.
4. Spoon the batter into the donut pans, filling each well about 3/4 of the way full. Bake for 10 minutes or when the donuts begin to lightly brown. Let donuts sit at room temperature for 5 minutes, then turn them out onto a cooling rack. Let cool completely at room temperature before glazing.

Blueberry Glaze

1. In a medium saucepan, combine blueberries, lemon juice and water over medium-high heat and bring to a simmer. Allow blueberries to simmer for about 5 minutes or when the blueberries have softened.
2. Pour the cooked blueberries through a fine mesh strainer into a medium mixing bowl (use a spatula to push as much of those juices through). Add the powdered sugar, salt and vanilla and whisk until smooth and creamy. If glaze is too runny, add more powdered sugar 1/2 tbsp at a time. If glaze is too thick, add more water 1/2 tbsp at a time.
3. Dip the cooled donuts into the glaze, coating well. Place donuts, glaze side up, back on the cooling rack and allow the glaze to firm up for about 5 minutes. Enjoy!