Iced Oatmeal Cookie Bars (Little Debbie Copycat!)

Name: Iced Oatmeal Cookie Bars (Little Debbie Copycat!)
Prep time: 5 min
Cook time: 25 min
Total time: 30 min
Cuisine: American
Ingredients: 1/2 cup unsalted butter (melted); 1 large egg; 1 cup light brown sugar (packed); 2 tablespoons medium (dark, or full-bodied molasses); 1 tablespoon vanilla extract; 1/2 teaspoon salt; 1/4 teaspoon cinnamon; 1 cup instant oats (not old-fashioned or whole-rolled); 3/4 cup all-purpose flour; 1/2 cup unsalted butter (softened); 1 1/2 cups confectioners’ sugar; one 7-ounce jar marshmallow creme; 1/4 to 1/2 teaspoon salt (cuts some of the sweetness)