Shred the yellow squash and place it in a clean kitchen towel or cheesecloth, then squeeze firmly to remove as much moisture as possible—this is crucial for preventing soggy pancakes. In a blender, combine the squeezed squash with the butter, eggs, and milk, blending until completely smooth and well combined. This wet mixture will form the foundation of your batter.
In a medium bowl, whisk together the flour, sugar, salt, baking powder, and cinnamon. I find whisking rather than just stirring ensures the baking powder distributes evenly, which gives you more consistent rise throughout the pancakes. Set this dry mixture aside.
Pour the squash mixture from Step 1 into the bowl with the dry ingredients from Step 2, gently folding together with a spatula until just combined—don't overmix, as lumps in the batter will create fluffier pancakes. Let the batter rest for 2-3 minutes while you prepare your cooking surface; this allows the baking powder to begin activating and the flour to fully hydrate.
Heat a griddle or large non-stick skillet over medium-high heat (around 350°F if you have a temperature-controlled griddle) and lightly butter or oil the surface. Once hot, pour the batter into 3-4 inch circles and cook for 2-3 minutes until bubbles form on the surface and the edges look set. Flip carefully and cook the other side for another 1-2 minutes until golden brown. I like to work in batches rather than crowding the griddle, which helps each pancake cook evenly.
Transfer the cooked pancakes to a warm plate and serve immediately with your favorite toppings—these are delicious with maple syrup, sour cream, or fresh berries.