Melt the butter, cool slightly, then whisk together the butter and the egg in a medium-large mixing bowl. Whisk in the buttermilk.
2 tablespoons unsalted butter, 1 large egg, 1 ⅓ cup buttermilk
Add the oat flour, ground flax seed (if using), sugar, baking powder, and salt to the bowl. Whisk until smooth. Allow batter to rest for 5 minutes. It will be quite thick.
While the batter is resting, preheat an electric griddle to 375ºF or a large frying pan over medium-low heat. If you like, add butter or oil to fry the pancakes.
Pour about ¼ cup batter onto the preheated griddle/pan. Cook until the pancakes are golden brown on the first side; flip and cook 1 minute more, or until done.
Notes
Make oat flour: If you don’t have pre-ground oat flour, you can make your own. Add regular or quick cooking oats to a blender or food processor. Process the oats, stirring occasionally, until they become a fine flour, about 1 to 2 minutes. Approximately 1½ cups oats will yield 1¼ cups oat flour.
Larger pancakes: Use ½ cup of batter per pancake. You'll end up with 5 large pancakes.
Thinner pancakes: Add a couple of tablespoons of regular milk to thin the batter to the desired consistency.
Storage: Cool pancakes completely, preferably on a wire rack, before storing. Refrigerate leftover pancakes in a covered container for up to five days. They can be frozen for up to a month.