In a medium mixing bowl, combine the 2 cups milk or nondairy milk with 2 cups of cereal. Let soak for at least 1 hour or up to overnight, covered in the fridge. Strain the milk through a fine-mesh metal sieve to get 1 cup of cereal milk.

Heat a small saucepan over medium heat. Add 4 tablespoons of the butter and stir frequently as it starts to melt and bubble. Look for little brown specks to start to appear and the color to change from yellow to a light amber, 3 to 5 minutes. Once it’s lightly browned, remove from the heat and transfer to a heatproof container to cool.

Preheat the oven to 350°F. Grease a 9-inch square baking pan or cake pan. In a large mixing bowl, whisk together the eggs, 1 cup of cereal milk, coconut milk, maple syrup, and vanilla until smooth. Add in the Mochiko rice flour, 1 cup of the granulated sugar, baking powder, and ½ teaspoon of the kosher salt and whisk until it becomes a smooth batter. Pour in the browned butter and continue to mix until incorporated. Pour the batter into the prepared pan.

In a bowl, crush the remaining 3 cups of cereal with your hands. Melt the remaining 4 tablespoons butter, then pour it onto the crushed cereal. Mix in the remaining 2 teaspoons of sugar and ½ teaspoon salt. Top the batter evenly with the crushed cereal mixture.

Bake for 1 hour. You’ll know when it’s done if you stick a chopstick in it and it comes out clean. Cool completely (about 30 minutes or so) then cut into squares, sprinkle with some powdered sugar and flaky salt if you wish, and serve. Store covered and enjoy within 3 days.