Meanwhile, prepare the frosting: In a medium saucepan, melt butter over medium heat. Stir in the brown sugar and heavy cream, stirring constantly until the sugar dissolves. Leave on the heat and let bubble for 3 minutes, then remove from heat, stir in the salt and vanilla, then let cool for 10 to 15 minutes, just until the caramel nears room temperature. Slowly beat in the powdered sugar. Frost cookies and top with pumpkin seeds right away, then enjoy.