Preheat oven to 250 degrees.
Spread brioche cubes on baking sheet and bake 45-60 mins until toasted and crispy.
Cool.
In a large pot, melt 6 tablespoons butter over medium heat.
Add onion, celery and garlic.
Cook 10 mins.
Add parsley, salt/pepper.
Add brioche cubes and 1½ cups broth and stir gently to combine.
In a medium bowl, whisk together remaining 1½ cups broth and eggs.
Add to pot with brioche and stir gently to combine.
Transfer mixture to a greased 9"x13" baking dish.
Melt remaining 2 tablespoons butter and drizzle over mixture.
Cover with foil and bake for 40 minutes.
Remove foil and bake uncovered for 40 more minutes or until the top is golden brown.