2 tablespoons (30 milliliters) Italian peach liqueur (or substitute with any peach liqueur)
1 cup (240 milliliters) sugar
1/2 cup (120 milliliters) melted butter
1/2 cup (120 milliliters) milk
1 teaspoon (5 milliliters) vanilla extract
4 eggs, whisked
4 cups (960 milliliters) flour
1 tablespoon (15 milliliters) baking powder
Glazes and finish:
2 cups (480 milliliters) sugar
2 cups (480 milliliters) water
1 cup (240 milliliters) caster sugar, plus more if needed (or substitute with regular sugar)
Fresh mint leaves
For the pastry cream:
add whole milk and lemon zest to a saucepan and cook over medium heat to a low simmer. Remove from heat. Whisk egg yolks in a bowl, then add sugar and flour and whisk together. Slowly drizzle half of the heated milk into the yolk mixture, while whisking vigorously, to temper. Transfer the yolk mixture to the remaining milk in the saucepan and place saucepan back over medium heat, whisking continuously until cream thickens and starts to bubble. Remove from heat and whisk in butter and peach liqueur.
Transfer warm pastry cream to a bowl and press plastic wrap down directly on the surface of the pastry cream. Refrigerate until cool (at least two hours).
For the cookies:
Preheat oven to 350 F (175 C).
Add sugar, melted butter, milk, and vanilla extract to a bowl and mix to combine. Add eggs and stir to combine. In a separate bowl, sift together flour and baking powder. Gradually add dry ingredients to wet, mixing until dough is smooth. Form dough into round, walnut-sized balls and place on parchment paper-lined baking sheets. Bake for 12-15 minutes or until bottom is slightly toasted. Transfer cookies to cooling rack and set aside to cool for 10-15 minutes.
Using a spoon, scoop out part of the middle of the flat-bottomed side of each cookie to make space for the pastry cream. Using an icing bag or a spoon, add one to two teaspoons (five to ten milliliters) of filling to the hollowed-out part of each cookie. Press two cookies together (flat sides meeting) to create peach shape.
For the glazes:
Add sugar and water to a small saucepan over medium heat until slightly thickened, but still clear, about eight to ten minutes.
Using a pastry brush, brush syrup over entire cookie, coating it completely. While the cookies are still wet with syrup, roll gently in castor sugar. Garnish with a clove to resemble a stem, and with fresh mint leaves to resemble leaves; Refrigerate cookies to set and chill before serving.