01 -
Heat milk in a medium saucepan over medium-low heat just until steaming, then reduce heat to low.
02 -
In a large bowl, whisk together egg yolks, sugar, lemon zest, salt, vanilla, and cornstarch until smooth and pale yellow.
03 -
Gradually add 1/4 of the heated milk to the egg mixture while whisking vigorously, then incorporate the remaining milk.
04 -
Transfer mixture back to saucepan and cook over medium-low heat for 8-12 minutes, whisking continuously until thickened to soft peaks consistency.
05 -
Remove from heat, transfer to a bowl and stir in butter until combined. Cover with plastic wrap directly on surface and refrigerate until completely chilled.
06 -
Combine sugar and lemon zest in a bowl, mixing well to infuse the flavors. Set aside.
07 -
Preheat oven to 175°C (350°F). Line two cookie sheets with parchment paper.
08 -
In a large bowl, whisk together flour, baking powder, baking soda, and salt. Set aside.
09 -
Using an electric mixer or stand mixer with paddle attachment, beat butter and granulated sugar on high speed until light and fluffy, about 2 minutes.
10 -
Mix in the egg, vanilla, and lemon zest on medium speed until pale and fluffy, 1-2 minutes.
11 -
Slowly incorporate the dry ingredients on low speed just until the dough comes together.
12 -
Scoop dough into balls using a large cookie scoop, roll in the prepared lemon sugar, then place on lined cookie sheets and slightly flatten each ball. Space cookies for even baking (6 per sheet).
13 -
Bake for 9-10 minutes, then let cool on the baking sheet for 5 minutes. For perfectly round cookies, use a circular cookie cutter to shape them immediately after removing from oven.
14 -
Move cookies to a cooling rack to cool completely.
15 -
Pipe chilled pastry cream onto cooled cookies using a piping bag fitted with a small circular tip.
16 -
Sprinkle about 1 teaspoon of sugar over each cream-topped cookie and caramelize with a kitchen torch until golden brown with a marshmallow-like aroma.
17 -
Allow the caramelized topping to cool for 10 minutes before serving. For best texture, add pastry cream and brûlée topping just before serving as cookies will soften after a few hours.