In a large bowl, whisk together the all-purpose flour, granulated sugar, baking powder, baking soda, and salt.
In a separate medium bowl, whisk the buttermilk, egg, melted unsalted butter, and vanilla extract until combined.
Pour the wet ingredients into the dry ingredients and stir gently until just combined. Do not overmix; a few lumps are okay.
In a small bowl, mix the softened cream cheese with powdered sugar until smooth and creamy.
Preheat a non-stick skillet or griddle over medium heat and lightly coat with cooking spray.
Spoon about 1 tablespoon of pancake batter onto the skillet to form a small circle.
Add about 1/2 teaspoon of the cream cheese mixture on top of the batter, then sprinkle a few pieces of fresh blueberries and diced strawberries over the cream cheese.
Cover the filling with another tablespoon of pancake batter, gently spreading it to cover the filling.
Cook the pancake poppers for 2 to 3 minutes on the first side, until bubbles form on the surface and the edges look set.
Carefully flip the poppers and cook for another 2 minutes until golden brown and cooked through.
Transfer the cooked pancake poppers to a plate and repeat the process with the remaining batter and filling.
Serve warm with maple syrup or your favorite breakfast syrup.