In a large bowl, cream the softened butter, 3/4 cup granulated sugar, and brown sugar together until light and fluffy (2-3 minutes). Beat in the egg, egg yolk, vanilla extract, and vanilla bean paste.

In a separate bowl, whisk together the flour, cornstarch, baking soda, and salt. Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined.

Cover the dough and chill in the refrigerator for at least 30 minutes.

Preheat oven to 350°F (175°C). Line two baking sheets with parchment paper.

Scoop dough into 1.5-tablespoon balls, placing them 2 inches apart. Gently flatten the tops. Bake for 10-12 minutes, until edges are lightly golden. Let cool on the baking sheet for 5 minutes before moving to a wire rack to cool completely.

Once completely cool, sprinkle about 1/2 teaspoon of the remaining granulated sugar evenly over each cookie.

Using a kitchen torch, move the flame continuously over the sugar until it melts and turns a deep amber color. Alternatively, place cookies under a preheated broiler for 30-60 seconds, watching constantly. Let the topping cool and harden for a few minutes before serving.