In a large bowl, vigorously whisk together the all-purpose flour, granulated sugar, baking powder, and salt. Make sure there are no lumps in the dry mixture. This step aerates the flour, contributing to ultimate fluffiness.
In a separate medium bowl, whisk together the milk, large egg, melted butter, and vanilla extract until well combined. Ensure your melted butter isn’t too hot, as it could scramble the egg.
Create a small well in the center of your dry ingredients. Pour the wet mixture into the well. Use a rubber spatula to gently fold the ingredients together until they are just combined. It is crucial to avoid overmixing; plenty of lumps in the batter are a good sign and will result in tender, fluffy pancakes.
Heat a lightly greased skillet or griddle over medium heat. Once hot, add ¼ cup of the batter for each pancake. Cook for approximately 2 minutes, until you observe the edges firming up and numerous bubbles beginning to rise and pop on the surface. Add a few frozen strawberries to each pancake. Carefully flip each pancake with a spatula and cook for another 2 minutes, or until golden brown and cooked through.