This recipe is for crispy, crumbly diamant cookies made with plenty of Earl Grey tea leaves. Mix unsalted butter and granulated sugar together, then add egg yolk, cake flour, and finely chopped Earl Grey tea leaves to make the dough. After letting the dough rest in the refrigerator, shape it into a round log, sprinkle with granulated sugar, and cut into 1cm wide slices. Bake in a 170°C oven for 20 minutes. Once baked, let the cookies cool slightly, then individually wrap them, making them perfect as a small gift or souvenir. With their rich tea aroma, these cookies are irresistible for tea lovers.