Heat griddle to 375 degrees. Whisk together flour, baking powder, baking soda, salt, and sugar in a medium bowl. Add eggs, buttermilk, and 4 tablespoons butter; whisk to combine. Batter should have small to medium lumps.
Heat oven to 175 degrees. Test griddle by sprinkling a few drops of water on it. If water bounces and spatters off griddle, it is hot enough. Using a pastry brush, brush remaining 1/2 teaspoon of butter or reserved bacon fat onto griddle. Wipe off excess.
Using a 4-ounce ladle, about 1/2 cup, pour pancake batter, in pools 2 inches away from one other. When pancakes have bubbles on top and are slightly dry around edges, about 2 1/2 minutes, flip over. Cook until golden on bottom, about 1 minute.
Repeat with remaining batter, keeping finished pancakes on a heatproof plate in oven. Serve warm.