famed pastry chef Pierre Hermé. I combine everything but the butter in a stainless steel bowl and cook it over simmering water, whisking constantly, as one would for a sabayon. When it’s thickened to the consistency of thin mayonnaise, I remove it from the heat and whisk in the softened butter and citrus zest. Hermé actually puts
the custard in a blender and then adds the butter. Either way, the result is a very creamy curd that makes an ideal filling for tarts or, in this case, crunchy, green-hued macarons. As an optional garnish for the macarons, I brushed the tops of some with a little watered down gel color and let it dry.