Mix the milk of choice with the vinegar and set aside to curdle a bit if doing a vegan version.
Preheat oven to 350 degrees, and prepare 12 muffin tins with grease or paper baking liners.
In the bowl of a food processor (I LOVE mine and use it all the time!), place all the dry ingredients and process to a fine powder.
Once everything is like a flour, add in all the wet ingredients, pulsing multiple times to blend. If the mixture seems a bit thin, let it rest a couple minutes to absorb a bit of the liquid....it's ok to add some flax meal or additional oats if needed.....
Pulse in any add ins you prefer.
Fill muffin tins 2/3 full, and bake in a preheated oven for 15-18 minutes. Tops should be set and not squishy.