Preheat oven to 400 degrees F. Oil a 1 ½ inch deep, 9-inch tart pan with a removable bottom (or a 9-inch pie pan).

In a medium bowl, whisk together 1/2 cup flour and the flax seed. Stir in the quinoa and butter, mixing well. Spread into the tart pan or pie plate, pressing down on the bottom and along the sides. Bake for 20 minutes until the crust is slightly dry and par-cooked. Set aside.

In a large sauté pan, heat olive oil over medium heat. Add the onions and celery and cook, stirring occasionally, for about 8 minutes, or until the vegetables are soft. Add the garlic and cook 2 more minutes.

Transfer the cooked veggies to a large mixing bowl.

In that same sauté pan over medium heat, cook the sausage for 8-10 minutes, until brown and fully cooked. Break up the sausage with a spatula while cooking.

Transfer the cooked veggies back into the sauté pan with the sausage.

Add chicken broth, thyme, sage, parsley, and egg into the mixture. Salt and pepper to taste. Once combined, remove from heat.

In a medium pot, place sweet potatoes and add water to cover.

Turn to high heat and bring to a boil. Once boiling, reduce the heat to low and simmer until potatoes are soft.

Drain water and return potatoes to the pot. Stir in 2 tablespoons olive oil, ½ tsp salt, and ½ tsp pepper, mashing until fluffy and no big chunks remain.

Transfer the filling mixture into the crust and spread the sweet potato mixture on top.

Bake until pie is hot and top is lightly browned, 25 to 30 minutes.

Let cool 10 minutes. Sprinkle with the parsley and serve.