Butterscotch Oatmeal Sandwich Cookies

Ingredients:

For the cookies:

1 & 1/4 cups all-purpose flour
1 & 1/2 teaspoons ground cinnamon
1/2 teaspoon baking powder
1/2 teaspoon salt
3 cups rolled oats
3/4 cup unsalted butter, softened
1 cup packed light brown sugar
2 large eggs
1 teaspoon vanilla extract

For the frosting:

1 cup packed light brown sugar
1/2 cup unsalted butter
1/4 cup heavy cream
1 teaspoon salt
1 teaspoon vanilla extract
1 & 1/2 cups confectioners' sugar

Directions: