Dulce de Leche and Nutella Thumbprints

INGREDIENTS

• 4 sticks of unsalted butter, at room temperature (1 lb.)
• 1 1/3 cups of sugar
• 1 ¼ tsp. vanilla
• ½ tsp. salt
• 4 ½ cups all-purpose flour
• 1 - 13 oz. can Nestle La Lechera, Dulce de Leche (caramel)
• 1 small jar Nutella
• Course sea salt for sprinkling