In a small saucepan, warm the milk over medium-low heat until steaming but not boiling, about 2-3 minutes. Remove from heat, add the lavender buds, and steep for 5-7 minutes. Strain through a fine-mesh sieve, pressing gently to extract all liquid. Discard the lavender.

In a microwave-safe bowl, whisk together the sweet rice flour and sugar until no lumps remain. Add the lavender-infused milk, honey, and vanilla extract, whisking until completely smooth.

Cover the bowl loosely with plastic wrap, leaving one corner open for steam to escape. Microwave on high for 2 minutes, then stir vigorously with a wet spatula to incorporate any dry spots.

Microwave for another 1 minute, stir again, then microwave for a final 30 seconds. The mochi is done when it becomes translucent, glossy, and pulls away from the sides of the bowl.

Generously dust a clean work surface and your hands with potato starch. Turn the hot mochi out onto the surface and dust the top liberally with more starch.

Let rest for 3-4 minutes until cool enough to handle comfortably. Gently flatten into a 1-inch thick rectangle using your palms, adding more potato starch as needed to prevent sticking.

Cut into 12 equal squares or use a round cutter for circles. Dust each piece with additional potato starch, shaking off any excess. Serve immediately for the softest texture, or let cool completely before storing.