• Preheat oven to 425 degrees f.
• Pour neutral oil into the baking sheet and brush all over the bottom and the sides, making sure to coat well.

Make the pancake batter

• In a large bowl, whisk together flour, baking soda, baking powder, salt and sugar.
• In a separate bowl, whisk together melted butter, eggs, buttermilk and vanilla.
• Add wet ingredients to dry ingredients and mix until combined. It's ok if the batter is a little bit lumpy, do not over-mix.
• Place the oiled baking sheet in the oven to preheat while you make the cinnamon swirl filling.

Cinnamon swirl filling

• In a small bowl, combine melted butter, brown sugar and ground cinnamon.
• Remove the preheated sheet pan from the oven and pour the pancake batter out onto the hot pan. Smooth it out to the edges with a spatula.
• Dollop the cinnamon mixture all over the batter and use a knife to swirl it through.
• Bake the pancakes at 425 degrees f for 15-20 minutes until the edges are golden brown and it looks puffed in the middle.

Icing

• While the pancakes are baking, make the icing. Whisk together powdered sugar, melted butter and milk until smooth.

Serving

• Cut the pancakes into squares and drizzle with icing.