Preheat and prep: Heat the oven to 350°F (175°C).
Line two baking sheets with parchment paper for even browning and easy cleanup.
Whisk the dry ingredients: In a medium bowl, whisk flour, cornstarch, baking soda, and salt until well combined. This prevents clumps and ensures even texture.
Cream the butter and sugar: In a large bowl, beat the butter and granulated sugar on medium speed for 2–3 minutes until light and fluffy. Proper creaming helps the cookies rise and turn out soft.
Add eggs and extracts: Beat in the egg, egg yolk, vanilla, and almond extract (if using) until smooth.
The extra yolk adds richness and enhances chewiness.
Combine wet and dry: Add the dry ingredients in two additions, mixing on low just until combined. If the dough looks dry or crumbly, mix in 1–2 tablespoons of milk or cream until it comes together. Do not overmix.
Shape and coat: Scoop the dough into 1 1/2-tablespoon portions (a medium cookie scoop works well).
Roll each portion into a ball, then roll in granulated sugar or sparkling sugar to coat.
Space and bake: Place dough balls on the prepared sheets, leaving about 2 inches between them. Bake for 9–11 minutes, until the edges are set and lightly golden but the centers still look soft and slightly underbaked.
Optional crinkle trick: For a gorgeous crinkle top, gently tap the baking sheet on the counter right after removing it from the oven.
Cool: Let cookies rest on the baking sheet for 5 minutes to finish setting, then transfer to a wire rack to cool completely. They’ll firm up as they cool but stay soft inside.