Bring a large pot of salted water to a boil.

Place the cumin seeds in a small skillet over medium heat and toast them, shaking the pan almost constantly. When you can smell the cumin, which should just take a minute or two, remove the pan from the heat and tip the cumin onto a small plate or into a small bowl to cool.

Place the butter in a large bowl.

Grind or mince the cumin seed and add it to the butter, along with the fleur de sel. Mix well.

When the water is boiling, plunge the corn rounds into it. As soon as the water returns to the boil, drain the corn, discarding the water. Immediately place the corn into the bowl with the butter and toss, toss, toss until the corn is covered with butter. Season with pepper, toss again.

Check the seasoning, adjust if necessary, then turn out the corn onto a platter and garnish with cilantro leaves.