Preheat oven to 325. Butter a 13x9x2-inch baking dish and set aside.
transfer stove top to a very large bowl.
Meanwhile, melt butter in a large skillet over medium-high heat; add onions Stir often until just beginning to brown, about 10 minutes. Sprinkle in poultry seasoning and sage. Set aside to cool. Add to bowl with stovetop; warm chicken broth and water. Cool. Whisk eggs. Add broth in with eggs. Add to stove top. fold gently until thoroughly combined. Add turkey pieces. Transfer to prepared dish, cover with foil, and bake until an instant-read thermometer inserted into the center of dressing registers 160°, about 15 to 25 minutes.