cup packed roughly chopped herbs (such as parsley, chives, or basil)
Preheat oven to 425 degrees.
Line a 15” x 10” rimmed baking sheet with parchment paper.
On a lightly floured surface, roll puff pastry to a dimension of 16” x 11”. It should come just up the sides of the pan. Prick all over with the tines of a fork. Lay a piece of parchment paper on dough and place a second baking sheet on top, to weigh down dough. You can also fill with pie weights or dried beans. Transfer to oven and bake 8 minutes, until dough is golden on the edges. Remove the second baking sheet or weights and parchment and return to oven. Bake for an additional 6-8 minutes, until dough is dry and puffed. Using your palm, flatten any parts of dough that have puffed, in order to accommodate the filling.
Meanwhile, place bacon in a medium skillet over medium-high heat. Cook, stirring, until bacon is crisp and fat is rendered, about 8 minutes. Remove with a slotted spoon to a paper towel-lined plate. Reserve 1/4 cup bacon fat. Add half of reserved fat to skillet and increase heat to heat. Add half of mushrooms, 3 sprigs thyme, and season generously with salt and pepper, and cook, stirring, until golden brown and beginning to crisp, about 8 minutes. Remove to a plate and repeat with remaining 10 ounces mushrooms, 3 springs thyme, and 2 tablespoons bacon fat.
Return first batch of mushrooms to skillet, add garlic, and remove from heat. Stir to combine, season to taste with salt and pepper, and let cool slightly.
In a large bowl, whisk cream cheese and half and half until smooth. Add eggs and whisk to combine. Add gruyere, parmesan, herbs, mushroom mixture, and bacon. Stir to incorporate. Transfer to baking sheet and spread mixture to the edges of the pan. Reduce heat to 375 degrees. Transfer pan to oven and bake until egg mixture is just set, about 28-32 minutes. Slice into squares and serve.