Place the turkey neck in a medium pot with 2 1/2 Cups of water. Cover and bring to a boil. Remove lid, reduce heat to low and simmer for 20-25 minutes, until meat can be pulled from turkey neck with forks. Turn off heat, set shredded turkey meat and stock aside, and discard turkey neck.
While turkey neck stock simmers, heat olive oil in a large sauté pan over medium heat. Add Mirepoix to pan and sauté for 20 minutes or until browned, stirring occasionally. Turn off heat and set aside.
For the roux: In a wide sauce pan, melt the unsalted butter over medium heat. Add flour and whisk vigorously until flour is fully incorporated with butter, being careful not to burn the mixture. Roux will darken slightly to a light caramel color.
Measure 2 cups of the turkey neck stock from pot and slowly incorporate into the roux, whisking constantly. Repeat the process with 1 cup TJ's Turkey Stock, incorporate slowly and whisk constantly. Add sautéed Mirepoix, salt, pepper and pan drippings (if desired) to the gravy and stir until combined. Reduce heat to low and simmer until desired consistency is reached. Serve immediately*.
*If dinner is not quite ready, keep gravy covered on the stove over low heat, stirring occasionally. Just before serving, add stock to thin gravy to desired consistency.