Traditional Shepard's Pie with Mushroom Powder

Ingredients:

6-8 c. Leftover Beef Stew/Pot Roast 
2 Tbsp. olive oil
1 onion, finely chopped
2 stalks of celery, chopped
2 Tbsp. flour (optional)
½ fresh mushrooms, torn apart (optional)
2-4 Tbsp. mushroom powder (we just dump it in)
1 c. frozen petite peas
3-4 c. beef stock
2 tsp. thyme 
1 tsp. sage
salt and freshly ground black pepper
3-4 c. mashed potatoes
2 c. shredded cheese (the stronger the cheese the better - a good cheddar or maybe some Dubliner Cheese)

Instructions:

In a large cast iron pan (or dutch oven), heat olive oil and then sauté onion and celery until soft, approximately 5 minutes. Add fresh mushrooms and continue to cook until mushrooms are just tender. Add flour and stir constantly for 2 minutes. Add leftover beef stew, beef stock, mushroom powder, all seasonings, and peas. Bring to a gentle simmer and cook for 15 minutes, stirring often. Turn off heat. Evenly spread the cheese over the cooked mixture (trust us...the cheese is better under the potatoes). Spoon mashed potatoes over the mixture. Bake at 375 degrees for 40 minutes or until the potatoes are golden brown. Enjoy!