Preheat griddle to 350F.
Add vinegar to a liquid measuring cup, then fill the rest of the measuring cup with milk until it reaches the 1.5 cup marker. Stir and let sit for 5-10 minutes to thicken. This is your "homemade buttermilk".
In a large bowl, whisk together flour, granulated sugar, baking powder, baking soda, and salt.
To dry ingredients, add homemade buttermilk, water, egg, vanilla extract, and melted butter.
Gently whisk the wet and dry ingredients together, just until incorporated and no dry patches of flour remain. There will still be small lumps in the batter. Allow batter to rest for 5 minutes before cooking.
Melt a little butter on the preheated griddle and use a spatula to spread it evenly across the surface. Add 1/2 cup of batter to the griddle for each pancake. Cook 2-3 minutes, until bubbles have started to form and pop on the surface. Flip pancakes and cook another 1-2 minutes, until golden brown and cooked through.
Remove pancakes from griddle and repeat process with remaining batter. Recipe makes 8-10 large pancakes. Serve warm with butter and syrup.