Spray a 10 inch x 14 inch x 3 inch casserole with cooking spray. Set aside.
Cut crust off cornbread.
Crumble into a large mixing bowl.
Crumble biscuits into bowl with cornbread. Set aside.
In a large skillet, melt butter over medium heat.
Add onion and celery.
Sauté until onions are translucent, about 5 minutes.
Add to bread mixture.
Add boiled eggs. Mix.
Stir in stock.
Season to taste with salt and pepper.
Add beaten eggs.
Pour into prepared casserole.
Bake until browned and puffy, about 90 minutes.
Notes
Don't mix everything ahead of time. It sours pretty quickly. If you're gonna prep this ahead of time, keep everything separated until you're ready to bake!
Keep an eye on this casserole while it's in the oven. You may need to cover with foil to prevent the top from burning while it bakes.
The casserole shouldn't be thick before you bake. It should be juicy.