Preheat the oven to 425 degrees Fahrenheit. Spray a 9 x 9-inch pan with nonstick cooking spray and set aside.
Prepare the cinnamon sugar filling by combining ½ cup packed brown sugar, 4 teaspoons ground cinnamon, and 3 tablespoons heavy cream in a small bowl, and set aside.
Add 2 ½ cups all-purpose flour, 1 tablespoon baking powder, 1 ½ teaspoons salt, and 2 tablespoons granulated sugar to a large bowl and whisk to combine.
Add 2 cups buttermilk to the flour mixture and stir until nearly fully combined. Add the cinnamon sugar mixture and stir it in just until the cinnamon is swirled throughout the batter, but not completely mixed together.
Add ½ cup melted unsalted butter to the bottom of the prepared baking pan. Add the biscuit dough to the pan and spread evenly.
Score the dough into 9 equal squares before baking. Bake for 28–32 minutes, until a toothpick inserted in the center comes out with a few crumbs.
Cream Cheese Icing
While the biscuits cool slightly, combine 2 ounces softened cream cheese and 2 tablespoons softened salted butter in a medium bowl until smooth.
Add 1 cup powdered sugar and mix until combined. Spread over the tops of the warm biscuits and serve immediately.
Notes
Leftover Instructions
Storage: Store leftover biscuits in an airtight container at room temperature for up to 5 days or in the refrigerator for up to 7 days.
Reheating: Reheat individual biscuits in the microwave for 15-30 seconds.
Freezing: Let the baked biscuits cool completely, then freeze them unfrosted in a freezer-safe container for up to 3 months. Thaw at room temperature for 2–3 hours, then top with fresh cream cheese icing.