In a medium bowl, combine baking powder, granulated sugar, and salt. Whisk until combined.
Add the egg and egg yolk. Whisk until the mixture is pale yellow and slightly foamy.
Add the buttermilk, flour, and two tablespoons of melted butter, stirring until just combined and slightly lumpy.
Optionally, let the batter rest for 20 to 30 minutes for fluffier, more tender pancakes.
Heat a large cast-iron skillet over medium-high heat until well preheated. An infrared thermometer should read between 350°F and 400°F.
Add 2 to 3 tablespoons of unsalted butter to the skillet and melt. Using a ¼-cup measuring scoop, portion the batter into the hot skillet. Cook for 3 to 4 minutes, until bubbles begin to form and the edges start to set.
Flip and cook for an additional 2 to 3 minutes, until the second side is golden brown and crisp. Add more butter to the pan as needed and adjust the heat as needed. Repeat with the remaining batter.
Notes
An optional 20 to 30 minute batter rest can make the pancakes lighter and fluffier.
For the best crispy edges, keep the skillet between 350°F and 400°F.
If the pan runs too cool, the pancakes can soak up too much butter and turn greasy.
Make sure the skillet stays coated in butter so the pancakes brown evenly and crisp around the edges.