In a large bowl, beat softened butter and granulated sugar until light and fluffy (~3 minutes).
Mix in the egg and vanilla extract until combined.
Gradually add flour and salt, mixing until a soft dough forms.
Divide dough into 2 discs, wrap in plastic, and refrigerate for 1 hour (to prevent spreading).
Preheat oven to 350°F (175°C). Roll dough to ¼-inch thickness on a floured surface.
Use a heart-shaped cutter to cut out cookies. Re-roll scraps for more cookies.
Place cookies on parchment-lined baking sheets. Bake for 10-12 minutes until edges are lightly golden.
Let cool on a wire rack. Dust with powdered sugar or decorate with icing/sprinkles.
