Preheat oven to 375 degrees F. Grease doughnut pans with cooking spray.
cooking spray
In a large mixing bowl, whisk together flour, baking powder, baking soda and salt until combined. Set aside.
1 cup all-purpose flour, 1-1/2 tsps. baking powder, 1/2 tsp. baking soda, 1/2 tsp. kosher salt
In another bowl, cream together melted butter, oil, sugar, brown sugar and vanilla until smooth. Beat eggs into the butter mixture.
1/4 cup unsalted butter, melted, 1/4 cup canola oil, 1/2 cup granulated sugar, 1/3 cup light brown sugar, 1-1/2 tsps. vanilla extract, 2 large eggs
Gently stir the dry ingredients into the wet ingredients, alternating with milk until fully incorporated. Do not overmix.
1 cup milk
Pour the mixture into a large piping bag (or Ziploc bag with one corner of the bag snipped off) and pipe the batter into each doughnut cavity about 3/4 full.
Bake for 8-10 minutes, or until the doughnuts are cooked through and a toothpick inserted in the doughnut comes out clean.
Allow the doughnuts to cool in the pan for 5-10 minutes before removing from the pan.