In a mixing bowl, combine 1 cup fine rice flour, 0.5 cup maida, 0.5 cup sugar, cardamom powder, pinch of salt, and black sesame seeds. Whisk well.

Pour in the thick coconut milk gradually, whisking smoothly with a hand whisk to form a lump-free, semi-thick ribbon-consistency batter (similar to dosa or pancake batter). Let the batter rest for 15 minutes.

Heat oil in a heavy deep kadai over medium flame. Submerge the iron or non-stick achu (rose cookie mold) directly into the hot oil for at least 5 to 7 minutes. The mold MUST be piping hot for the batter to adhere.

Carefully lift the hot mold from the oil, gently dab its base on a paper towel for 1 second to shed excess surface grease, and dip the mold into the batter.

CRITICAL RULE: Dip the mold only 3/4th of the way into the batter! Never submerge the top surface of the mold into the batter, or the cookie will cling to the top and will not release.

Immediately transfer the batter-coated mold into the hot oil. Hold the mold submerged without touching the bottom of the pan for 10 to 15 seconds.

Gently shake the mold up and down or nudge the edges lightly with a wooden skewer or fork. The flower-shaped cookie will slide off cleanly into the oil.

Deep fry on medium heat for 60 to 90 seconds, flipping once, until pale golden and crisp. Note: Achu murukku feels slightly soft when lifted from hot oil, but crisps up firmly into a brittle cookie as it cools.

Repeat the process: always return the empty mold into the hot oil for 30 seconds before dipping into the batter for the next batch.

Drain on paper towels, cool completely, and store in an airtight container.