Peanut Butter Oatmeal Sandwich Cookies

For the Cookies:

• 3/4 cup all-purpose flour
• 1/2 teaspoon baking soda
• 1/4 teaspoon baking powder
• 1/2 teaspoon salt
• 1/2 cup butter at room temperature, unsalted
• 1/2 cup peanut butter creamy
• 1/2 cup granulated sugar
• 1/2 cup light brown sugar packed
• 1 egg large
• 1 teaspoon vanilla extract
• 1 cup oats quick-cooking

For the Filling:

• 3 tablespoons butter at room temperature, unsalted
• 1/2 cup peanut butter creamy
• 1 cup powdered sugar sifted
• 3 tablespoons heavy cream