Combine the flour, sugar, baking powder, baking soda, and salt in a large bowl. Add the discard, milk, butter, eggs, and vanilla and stir to combine well. Be careful not to over-mix! The batter will be lumpy.Heat a large non stick skillet or griddle over medium heat (I use the 375 degree setting on my griddle). Add batter in ¼ cup scoops, being careful not to overcrowd. Cook for 1-2 minutes, until edges have firmed up and bubbles begin appearing on the tops of the pancakes. Flip and cook 1 minute more. Remove to a plate. Continue until all the batter has been used.Serve immediately with your favorite pancake toppings!