https://www.justonecookbook.com/butter-mochi/

1. Arrange a rack in the middle of the oven and preheat the oven to 375ºF (190ºC).
2. First, melt the butter with a liquid measuring cup in the microwave. Do 30 seconds bursts at a time, should be ~1 min total.
3. In a medium bowl, combine the mochiko (glutinous rice flour), baking powder, and salt and whisk to combine. It's important to equally distribute the baking powder and salt into the mochiko flour. Set it aside.
4. In a stand mixer bowl or a large bowl, crack the eggs and add the sugar. Whisk at low speed (by hand or on mixer Speed 2) the eggs and sugar together until creamy.
5. Add the unsweetened coconut milk and evaporated milk and stir to combine.
6. Add vanilla extract and butter and stir to combine.
7. Next, add the dry ingredients all at once to the mixing bowl and whisk to incorporate everything.
8. Grease a baking pan and pour the batter into the center of the prepared pan.
9. Bake at 375ºF (190ºC) for 45 minutes, or until an inserted skewer comes out clean. The mochi should be set and golden brown on top.
10. Let cool and slice.