Mise en Place: Bring butter to 65°F (18°C) and egg to room temperature.

Creaming: Cream the butter and sifted powdered sugar on medium speed for 3 to 4 minutes until pale and light.

Emulsify: Lower speed, gradually add the egg and vanilla extract, and mix until smoothly integrated.

Dry Blend: Add sifted flour and fine sea salt all at once. Mix on low speed just until the flour is absorbed. Do not overmix.

Pipe: Place dough into a pastry bag fitted with an open star tip. Pipe rosettes onto a parchment-lined baking sheet.

Chill: Refrigerate the piped cookies for 20 to 30 minutes to lock in the shapes.

Bake: Bake in a preheated convection oven at 350°F (175°C) for 12 to 15 minutes until edges are barely golden.

Cool: Rest on the baking sheet for 5 minutes, then move to a wire rack to finish cooling.