1. Prepare the ingredients
Start by measuring and preparing all the necessary ingredients. Also ensure you have the required utensils, such as bowls, whisks, and donut molds.

2. Prepare the donut batter
In a bowl, mix the melted butter and sugar until smooth. Then add the eggs and mix until you reach a smooth texture. In another bowl, combine the flour, matcha powder, and baking powder. Gradually incorporate this dry mixture into the previous mixture, stirring until a homogeneous batter is obtained.

3. Fill the molds
Pour the batter into the donut molds, ensuring it is evenly distributed.

4. Bake
Preheat the oven to 180°C (350°F), then bake the donuts for 12 to 15 minutes. The donuts are ready when their surface is slightly golden and they spring back when gently pressed.

5. Prepare the white chocolate
Melt the white chocolate in a double boiler or microwave. For the double boiler, place the chocolate in a heat-resistant container and set it over a pan of hot water. For the microwave, heat the chocolate in 15 to 20-second intervals, stirring each time, until smooth.

6. Decorate the donuts
Let the donuts cool after baking. Pour the melted white chocolate over their surface and add toppings like matcha powder or nuts according to your preference.