Preheat oven to 350°F. Grease a 9- x 13-inch casserole dish.

Sauté onions in a large sauté pan lightly coated with evoo, over medium-high heat, until medium brown and very soft. 

Add mushrooms to the pan and a bit more evoo. Sauté mushrooms until browned and crispy on edges. Add celery and garlic to the pan and continue to cook for 3 to 5 minutes until celery begins to soften.

Transfer vegetables to greased pan. Add matzo farfel, broth, dates, and egg yolks. Stir to combine. Season with salt and pepper. Cover with foil and bake at 350°F for 30 minutes. Uncover and bake 15 minutes more until lightly browned, or cool completely and freeze for up to 1 month.