Infuse the cream

• Heat part of the cream with the lemon zest until steaming, then remove from the heat.
• Let the zest infuse for a few minutes.

Melt the chocolate

• Pour the hot cream over the chopped white chocolate through a sieve.
• Let it sit, then stir until completely smooth.
• Stir in the lemon juice and the softened butter.

Chill the ganache

• Add the cold cream and stir until homogeneous.
• Cover with plastic wrap touching the surface and refrigerate until firm.

Whip the ganache

• Whip the chilled ganache with a hand mixer until light and fluffy.
• Fold in the poppy seeds.
• Pipe into macarons or use as a filling.