Make the Crepes:

1. Combine all the ingredients in a blender and mix until combined. Crepe batter is best if made a few hours in advance or even overnight.
2. Spread a bit of butter or oil in a nonstick skillet and heat until shimmering. I use a 10 or 12 inch skillet. Keep the heat on medium high.
3. Pour in a little less than 1/4 cup batter, tilting the skillet to distribute the batter over the surface of the skillet. Heat until lightly golden, 2-3 minutes, flip and cook for about 30 seconds – 1 minute. Cook all the crepes.
4. If not using immediately, stack cooked, cooled crepes and refrigerate, up to 3 days.
5. Crepes freeze really well too. Store them with parchment paper or wax paper in between crepes, in a large freezer ziplock bag, up to 3 months.

Make the Chicken and Mushroom Filling:

1. Heat the butter or oil in a skillet on medium high heat. Add the onions, seasoning with salt and pepper to taste. Cook until the onions have softened, about 5 minutes. Add the mushrooms, season with salt and pepper and cook for another 5-7 minutes, until the mushrooms are tender and golden. At first the mushrooms will exude a lot of liquid, but then eventually absorb it and begin to brown.
2. Add the cooked chicken, the onions and mushrooms to a food processor and pulse a few times until it’s all evenly mixed in very small pieces. You don’t want it to be a puree, but the chopped up chicken and mushrooms should be pretty tiny. Transfer to a large bowl.
3. Finely grate the hard boiled eggs on the small holes of a grater. (If you have a meat grinder, you can put the chicken, mushrooms and the eggs through the grinder instead of using the food processor.)
4. Season with salt and ground black pepper, if needed. Add the grated cheese and the chicken broth. You can add more or less broth, depending on how dry/wet the chicken and mushroom mixture is. The broth will help to keep the mixture together and later on when it is cooked, will help keep the filling from falling apart and from being too dry.

Assembling the Crepes:

1. Place about 1/4 cup of the filling on a crepe and gently spread it out thinly over the crepe, being careful not to rip the crepes. Roll up the crepe as tightly as you can. Place the filled crepe, seam side down in a large rimmed dish. Repeat with all the crepes and the filling. Keep the assembled crepes covered in the refrigerator for up to 3-5 days. You can also freeze the crepes for up to 6 months. Individually wrap each filled and assembled crepe in plastic wrap and then place the wrapped crepes in a large freezer ziplock bag.

To Serve:

1. In a nonstick skillet, melt some butter or oil and cook the crepes over medium low heat, until golden brown on both sides and warm all the way through, about 3 minutes per side. Serve with sour cream and garnish with fresh herbs, like green onions, dill, parsley, etc.