Preheat oven to 425 degrees. Butter 14 holes of three doughnut tins and set aside. In a mixing bowl, whisk together flour, baking powder, baking soda and salt for 30 seconds, set aside.
In a separate mixing bowl, using an electric hand mixer, blend together melted butter, vegetable oil, sugar and vanilla bean seeds until smooth, about 1 minute. Blend in eggs one at a time then mix in vanilla extract.
Working in three separate batches, beginning and ending with flour mixture, add 1/3 of the flour mixture alternating with half of the milk and mix just until combined after each addition. Spoon batter into buttered doughnut wells, filling them about 1/4-inch from the rim.
Bake in preheated oven 7 - 8 minutes, or until toothpick inserted into doughnut comes out clean. Transfer to a wire rack to cool until lukewarm then dip in glaze and return to wire rack, immediately top with sprinkles if using and allow glaze to set at room temperature.
For the glaze:
In a flat bottomed bowl, whisk together powdered sugar, melted butter, vanilla and salt then stir in 2 Tbsp of milk, adding additional milk 1 tsp at a time to reach desired consistency and whisk until smooth. Tint with food coloring if desired.
Warm in microwave in 6 - 10 second intervals on HIGH power to warm as it begins to set while dipping doughnuts, as needed, whisking after heating.