1. Add the white chocolate and heavy cream to a heatproof bowl and warm gently until melted, then stir in the vanilla extract and let the filling cool until slightly thickened.

2. In a mixing bowl, whisk together the sweet rice flour and granulated sugar.

3. Pour in the milk and melted butter, then mix until the batter is completely smooth and free of lumps.

4. Lightly grease a pan or baking dish and spread the batter into an even layer.

5. Cook until the dough is set and tender, then let it cool just enough to handle.

6. Cut the cooked dough into equal rectangles or squares.

7. Spoon a small amount of the white chocolate filling into the center of each piece.

8. Fold or roll the dough over the filling and press gently to seal the shape.

9. Lightly brown the tops if desired for color, then dust with powdered sugar before serving.