Preheat and Grease Pan:
Heat oven to 425°F (220°C). Grease a 9x13-inch rimmed sheet pan with nonstick spray, covering sides and corners thoroughly. Set aside.Whisk Dry and Wet Ingredients:
In a large bowl, combine flour, brown sugar, granulated sugar, baking powder, and salt with a whisk. Add eggs, milk, melted butter, and vanilla; whisk until smooth and fully blended.Transfer and Level Batter:
Transfer batter to the prepared pan. Gently tap the pan on the counter several times to level and flatten the batter.Swirl Strawberry Jam and Top:
Mentally split the batter into four equal quadrants. In one quadrant, drop teaspoons of strawberry jam and use a toothpick to swirl it into a marble pattern. Arrange sliced strawberries on top.Scatter Blueberries:
In another quadrant, scatter blueberries. In a third quadrant, sprinkle chocolate chips.Add Chocolate Chips:
For the remaining quadrant, mix melted butter, brown sugar, and cinnamon. Drop teaspoons of this mixture and swirl with a toothpick to create a marbled effect.Swirl Cinnamon Butter Mixture:
Bake for 15-18 minutes, until a toothpick inserted in the center emerges clean and the pancake rebounds when lightly pressed.Bake Until Golden:
Let cool for about a minute, then cut into portions. Serve with syrup, butter, powdered sugar, or any combination.