Preheat your oven to 375°F (190°C) and lightly grease an 8x8-inch ceramic baking dish. In a large bowl, whisk together the warm milk, eggs, pure maple syrup, 2 tablespoons melted butter, and vanilla extract. Stir in the old-fashioned rolled oats, baking powder, cinnamon, and kosher salt. Pour into the prepared baking dish.

In a small bowl, stir together the 3 tablespoons softened butter, packed dark brown sugar, and 1 tablespoon ground cinnamon until a thick paste forms. Drop spoonfuls of the cinnamon-sugar paste over the oat batter and use a butter knife to swirl it in figure-eight patterns.

Bake uncovered for 20–22 minutes until the edges are golden brown, the center is puffed and set, and the cinnamon swirl is bubbling.

While the oatmeal bakes, whisk the softened cream cheese, powdered sugar, 2 tablespoons milk, and vanilla until smooth and pourable. Let the baked oatmeal cool for 5 minutes, then drizzle generously with the warm cream cheese glaze and slice into 6 squares.