Boil water in a saucepan. Set aside.
In a medium mixing bowl, add white chocolate chip. If you are using white chocolate blocks, make sure to chop beforehand. This allows the chocolate to melt easily.
Melt the chocolate in a double boiler by placing the heat-resistant bowl on top of the saucepan. Stir often and watch it melt. Remove bowl from the heat once the chocolate is melted to prevent burning.
Sift in your preferred tea powder (matcha, houjicha, or genmaicha) into the melted white chocolate. Use a spatula to mix until combined with no clumps.
In a small saucepan, heat the whipping cream over medium-high heat, until bubbles start showing on the edge. This should take less than 30 seconds, so do not leave it unattended. Do not boil the whipping cream.
Pour the whipping cream into the melted chocolate. Use a spatula to mix until combined with no clumps.
Wrap the bowl, touching the surface of the chocolate, with a plastic wrap. Freeze for 30-35 minutes (max 30 minutes if you are using a whisk; max 35 minutes if you are using a hand mixer).
Whisk (preferably using a hand mixer) the chocolate mixture until stiff peak. This should take less than 30 seconds with a hand mixer, or about 100 times using a whisk.
Line a baking sheet (or plates that can fit into your freezer) with parchment paper.
Prepare the piping bag with the piping tip. Put the chocolate into the piping bag and remove all excess air using a plastic scraper. Pipe on to the lined baking sheet. It can turn into a vertical ribbon-like shape. If you do not have a piping tip, you can cut the piping bag to create a big, round tip. Pipe into a ball shape and try to do each piping in one go. This will help with shaping later.
Put in the freezer for 1 hour or overnight. Dust with your preferred tea or cacao powder. Ready to serve.