Buttery Thumbprint Cookies with Jam - chefmelt

Ingredients

• 1/3 cup (105g) jam or preserves.
• 2 teaspoons cornstarch.
• 1/2 teaspoon salt.
• 1/3 cup (70g) sugar.
• 3/4 teaspoon vanilla extract.
• 1/2 cup sugar for rolling (if desired).
• 1 large egg yolk.
• 1/3 cup (70g) tightly packed light brown sugar.
• 2 1/4 cup (280g) all-purpose flour.
• 1 cup (226g) unsalted butter, softened and at room temperature.