Place a clean coupe glass into the freezer or fridge to chill. (Do not do this step more than five minutes in advance so that the glass doesn't get too cold and shatter!)
Add matcha powder to hot water and mix vigorously to dissolve, using a bamboo whisk, fork, or milk frother.
Add prepared matcha to a cocktail shaker, followed by almond milk, gin, and amaretto.
Fill cocktail shaker halfway with ice, seal, and shake vigorously until chilled to the touch (about 8 seconds).
Shake and strain into chilled coupe making sure to get as much liquid and foam into the glass.
Grate fresh nutmeg over top and serve immediately.