Preheat oven to 325F/165C.

Grease 6 cups in a muffin tin with room temperature unsalted butter. Set aside.

Combine glutinous rice flour, matcha powder, baking powder, and salt in a bowl and whisk together.

In a medium mixing bowl or 1-quart measuring cup, whisk together milk, egg, honey, melted butter, and vanilla extract.

Add dry ingredients to wet ingredients and whisk well until smooth. The consistency should be thick, but runny, like a syrup. Add more milk, a tablespoon at a time, to achieve the proper consistency, if needed.

Divide the matcha mixture equally among the 6 muffin cups.

Bake for 25-30 minutes.

Let cool for 10 minutes in the pan before carefully removing the bites to a cooling rack to cool completely. Mochi bites come out of the oven puffy, but will sink as they cool.

Dust with icing sugar or drizzle with melted chocolate, if desired.

Store in a sealed container at room temperature for 2-3 days max for best results.