In a large bowl, whisk together flour, sugar, baking powder, baking soda, and salt.
In another bowl, beat egg, buttermilk, vanilla, and melted butter until smooth.
Pour wet ingredients into dry ingredients and mix gently until just combined. Do not overmix.
Adjust consistency with milk if needed. Batter should be thick but pourable. Let rest for 5 minutes.
Grease a bunny-shaped pancake mold with butter or oil.
Heat a non-stick pan over medium-low heat and lightly grease.
Place mold on pan and fill halfway with batter.
Cook for about 2 minutes until bubbles form and edges set.
Carefully remove mold and flip pancake. Cook another 1–2 minutes until golden.
Repeat with remaining batter.
Serve with powdered sugar, butter “tails,” and maple syrup.