• Pre-heat oven to 450 degrees. Place an 8-10” cast iron pan in the oven on the middle rack while the oven is preheating. This will allow the pan to get very hot.
• While the oven is preheating, make the batter. Place the 3 eggs and 1 egg white in the blender and blend on high speed until the eggs turn light and frothy, about 2 to 3 minutes. Then add 3/4 cup oats, 2/3 cup milk, 1/4 teaspoon baking powder, 1 teaspoon vanilla extract, 1/2 teaspoon ground cinnamon, and 1/8 teaspoon kosher salt. Blend on high speed for another 1 to 2 minutes, or until the batter is very smooth (no lumps) and well combined. The batter will be thin, no worries.
• Carefully remove the hot pan from the oven (be sure to use pot holders/oven mitts because the pan will be very hot) and place the 4 tablespoons of cubed butter in the pan, it will immediately bubble and begin to melt. Place the skillet back in the oven until the butter just begins to brown (it will smell nutty and fragrant) for 30-45 seconds, watching carefully to avoid burning the butter!
• Remove the pan from the oven again and swirl the butter so it coats the pan evenly. Working quickly, pour the batter into the center of the pan and immediately place pan back into the oven. Bake for 10 minutes at 450 degrees, then lower oven temperature to 400 degrees and cook for an additional 10 minutes or until the Dutch baby has risen substantially and is golden brown. Approximately 20 minutes total.

Caramel Sauce

• While the dutch baby is baking, prepare the caramel sauce. Simply combine 1 cup light brown sugar, 1/2 cup heavy cream, 1 tablespoon simple syrup, 4 tablespoons butter and 1/4 teaspoon koshersalt in medium-sized pan. Cook over medium heat for about 8-10 minutes, stirring occasionally with a spatula. The caramel will look a bit thin but as it cools it will begin to thicken. Once it somewhat cools, transfer to a small serving bowl.

To Serve

• Remove pan from the oven and dust the Dutch baby with confectioners sugar. (You'll be serving directly from the pan which is very hot. Place skillet on a trivet.) Drizzle with the caramel sauce and serve immediately.