Preheat the oven to 350°F (175°C). Lightly grease a mini muffin tin with cooking spray.
In a medium bowl, whisk together the flour, granulated sugar, baking powder, baking soda, and salt.
In a separate bowl, whisk the buttermilk, egg, melted butter, and vanilla extract until combined.
Pour the wet ingredients into the dry ingredients and stir until just combined. Do not overmix; the batter will be slightly lumpy.
In a small bowl, mix the softened cream cheese and powdered sugar until smooth.
Place about 1 tablespoon of pancake batter into each mini muffin cup, filling about halfway.
Add about 1 teaspoon of the cream cheese mixture on top of the batter in each cup.
Sprinkle a few pieces of diced strawberries and blueberries over the cream cheese layer.
Top each muffin cup with an additional tablespoon of pancake batter to cover the filling.
Bake in the preheated oven for 12 to 15 minutes or until the pancake poppers are golden and a toothpick inserted into the batter (not the filling) comes out clean.
Allow the pancake poppers to cool in the tin for 5 minutes before removing.
Serve warm and enjoy!