Boil water in a saucepan. Once it reaches a boil, set it aside.
In a medium mixing bowl, add white chocolate chips. If you’re using white chocolate blocks, chop them into small pieces beforehand to ensure they melt evenly.
Create a double boiler by placing the heat-resistant bowl with the chocolate over the saucepan of hot water. Stir the chocolate frequently as it melts. Once fully melted, remove the bowl from heat to avoid burning the chocolate.
Sift your preferred tea powder (matcha, hojicha, or genmaicha) into the melted white chocolate. Use a spatula to mix thoroughly until the mixture is smooth and free of clumps.
In a small saucepan, heat the whipping cream over medium-high heat until bubbles form along the edges, about 30 seconds. Be careful not to boil the cream.
Pour the heated whipping cream into the melted chocolate mixture. Stir with a spatula until the mixture is smooth and well-combined.
Cover the surface of the chocolate mixture with plastic wrap, pressing it directly onto the chocolate. Freeze the mixture for 30-35 minutes (30 minutes if you plan to whisk by hand; 35 minutes if using a hand mixer).
After chilling, whisk the chocolate mixture until stiff peaks form. This should take less than 30 seconds with a hand mixer or about 100 vigorous strokes if whisking by hand.
Line a baking sheet or plates (that will fit in your freezer) with parchment paper. Prepare a piping bag with a piping tip, then fill the bag with the chocolate mixture, removing any excess air.
Pipe the mixture onto the lined baking sheet, forming either ribbon-like shapes or small balls. For a smooth shape, try to complete each piping motion in one continuous squeeze.
Freeze the piped chocolate for at least 1 hour or overnight. Before serving, dust the chocolates with your choice of tea or cocoa powder.