Vegetarian Mushroom and Croissant Bake

Name: Vegetarian Mushroom and Croissant Bake
Ingredients: 12 regular size croissants (torn little bit bigger than bite sized pieces); 4 tablespoons salted butter (divided (2+2)); 1 small onion (chopped); 3 cloves garlic (minced); 2 celery stalks (chopped); 8 oz baby bella mushrooms (chopped into large chunks); Salt and black pepper (to taste); 3 stalks of kale (stalks removed and leaves roughly chopped); 2 tablespoons fresh chopped thyme; 1 tablespoon fresh chopped rosemary; 2 cups vegetable broth; 2 eggs (beaten); 1 cup shredded cheese (I used Gouda, see notes)