Instructions: Preheat your oven to 350F 175C and grease a donut pan with cooking spray. In a mixing bowl, combine the glutinous rice flour, sugar, baking powder, and a pinch of salt. In another bowl, whisk together the milk, water, melted butter, vanilla extract, and egg. Slowly pour the wet ingredients into the dry ingredients and stir until well combined. Pour the batter into a piping bag or a plastic storage bag with a corner snipped off for easy piping. Pipe the batter into the greased donut pan, filling each cavity about 2/3 full. Bake in the preheated oven for 15-18 minutes, or until the donuts are firm and lightly golden on the edges. Remove the donuts from the oven and let them cool in the pan for a few minutes before transferring them to a wire rack to cool completely. Optional: Dust the cooled mochi donuts with powdered sugar or drizzle with a glaze of your choice. Enjoy your homemade Baked Mochi Donuts!