In a large bowl, whisk together the flour, baking powder and salt.
In another bowl, combine the milk, sour cream, vanilla bean paste and egg. Whisk together until smooth. Slowly pour the melted butter into the milk mixture while you continue to whisk.
Make a well in the flour mixture and pour in the wet ingredients. Stir with a wooden spoon until the batter is smooth. At this point, if the batter seems too thick, stir in a few tablespoons of milk. Transfer the batter to a squeeze bottle.
Heat a griddle over medium-high heat and spray with nonstick cooking spray. Pipe two 3-inch dollops of batter next to each other and just touching. Using a toothpick, drag the batter down to form the point of the heart. Add a few blueberries if using, gently pressing them into the batter. Continue with additional batter to make more pancakes. Wait until you see bubbles start to rise from the batter and peek underneath the pancakes to make sure they're uniformly golden brown. If so, flip! Continue cooking until the second side is golden brown. Continue with the remaining batter. Serve immediately.