1. Trim fat and membranes from giblets. Rinse giblets; pat dry. Add giblets and neck to pan with turkey. Roast until browned, about 30 minutes. Set aside.

2. Make a bouquet garni: Tie peppercorns, thyme, parsley, rosemary, and bay leaf in a square of cheesecloth. Set aside.

3. Make the stock: Melt butter in a medium saucepan over medium-high heat. Add vegetables. Cook, stirring, until beginning to brown, 7 to 10 minutes.

4. Reduce heat to medium; add giblets, neck, bouquet garni, and 1 quart water. Cover, and bring to boil. Reduce heat to medium-low, and cook, uncovered, until reduced to about 3 cups, 50 to 60 minutes. Pour mixture through a fine sieve into a clean medium saucepan. Keep stock warm over medium-low heat. Roughly chop giblets; shred meat from neck with a fork. Set aside. Discard other solids.

5. Transfer turkey to a large platter. Reserve 3 tablespoons drippings from pan. Pour remaining drippings into a gravy separator; let stand until separated, about 10 minutes. Discard fat.

6. Deglaze roasting pan: Place roasting pan over 2 burners. Add wine; bring to a boil, stirring with a wooden spoon to loosen any browned bits on bottom of pan. Reserve deglazed liquid.

7. Make the gravy: Put the reserved 3 tablespoons pan drippings from turkey in a medium saucepan; cook over medium heat until hot. Add the flour, whisking vigorously to combine. Cook, whisking constantly, until fragrant and deep golden brown, about 9 minutes. Whisking vigorously, slowly add hot stock. Bring to a boil. Reduce heat to a gentle simmer.

8. Stir in reserved deglazed liquid and separated pan juices. Add giblets and neck meat. Season with salt and pepper. Simmer, stirring occasionally, until the gravy has thickened to the consistency of heavy cream, about 20 minutes. Pour through a fine sieve into a saucepan; discard solids. Keep gravy warm over low heat. Season with salt and pepper.