Strawberry Filled Pancakes

In a large bowl, whisk together the flour, baking powder, salt, and sugar.In a small bowl, lightly whisk the egg yolks, then whisk in milk and gradually add melted butter while whisking non-stop to avoid curdling. Whisk the yolk mixture into the flour mixture until well combined (the batter will be somewhat lumpy).In a separate medium bowl, beat the egg whites with an electric mixer on high speed until medium-stiff peaks form (peaks are just stiff enough to stand up firmly but with a slight curl at the tip), about 2-3 minutes. Using a rubber spatula, gently stir the whites into the batter in two additions.Heat the Filled Pancake Pan over medium (or medium-low) heat and coat lightly with a cooking spray.Spoon 1 tablespoon of batter into each well, followed by 1 teaspoon of fruit preserves in the center of each pancake and top with additional 1 tablespoon of batter. Cook until the bottoms are golden brown and the edges are somewhat set, about 3-5 minutes. Using 2 wooden skewers (or forks but I found skewers work much easier), flip the pancakes over and cook until golden and crispy, about 3 minutes more. Transfer to a plate and repeat with the remaining batter.Sprinkle with powdered sugar (optional) and serve immediately with syrup, whipping cream, sour cream, greek yogurt, or just as is.