Blackberry Jam Shortbread Bars

Bahan-bahan (30 porsi)

• 1½ cups (3 sticks) butter, (at room temperature)
• 3/4 cup light brown sugar, (firmly packed)
• 3/4 cup granulated white sugar
• 2 teaspoons vanilla extract
• 3/4 teaspoon salt
• 3/4 cup almond flour ((or very finely ground almonds))
• 2¾ cups all purpose flour
• 1½ cups seedless blackberry jam
• powdered sugar, (for dusting)