preheat the oven to 375 degrees.
fill up a large pot with water, put on high heat and bring to a boil.
While that is warming up, cut off the ends of the green beans and put in a trash bowl. Cut the stalks of the green beans cut into 2-3 inch long pieces (so they can fit in your mouth without effort). Put a bowl and set aside waiting for the water to boil.
peel the outer layer of the shallot and put in the trash bowl. Cut the shallot into 4 pieces and set aside.
Crush and peel the garlic. Leave whole and set aside, separate from the shallot.
Cut your head of cauliflower into florets that are roughly the same size, this helps them steam evenly. Put in a bowl and set aside.
Take half of the mushrooms (8 ounces) and cut each mushroom head into 4 pieces. You can use the stalks if they are short. Otherwise, cut off and put in the trash bowl.
Take a medium-sized pot, place on the oven and turn on the heat to medium. Once the pot is hot add 2 tablespoons extra virgin olive oil. Coat the bottom of the pan and add the shallot and a tsp of salt. Stir the shallot and let cook for 3-4 minutes, stirring to prevent burning. Add garlic and cook for another minute.
Add 2 cups of bone broth, cauliflower, and the chopped mushrooms, stir and cover with a lid. Bring to a boil then turn down to medium-low heat to steam the cauliflower for about 8 minutes.
Once cauliflower is easily pierced with a fork, add 2 more teaspoons of sea salt, 3 tsp black pepper, and use your immersion blender or regular blender to blend into a smooth consistency (think cream of mushroom soup from a can). Add more bone broth if needed while blending. It will have a thicker consistency but it needs to be slightly runny versus the consistency of mashed potatoes.
Once the large pot of water is boiling, add the cut green beans for no more than 5 minutes.
While the green beans are being blanched, get a strainer and a large bowl of ice water ready. Once the timer goes off (you have to use a timer, trust me) strain the green beans then immediately put in the ice water to stop the cooking process. Leave in the ice water for a few minutes (you don't need a timer for this one), then strain out and leave in the strainer while you're finishing up everything else.
Take the remaining mushrooms and cut them into small pieces (around 8 cubes).
Preheat a large skillet on medium heat. Once hot, add 1 tbsp extra virgin olive oil. Add mushrooms and another tsp of sea salt. Cover with a lid for 2 minutes to steam, then stir to prevent burning and cover again for another 2-3 minutes. Once soft, turn off and remove from heat. Add to your "cream" of mushroom soup and stir in with a spoon. Do not blend!
Take your casserole dish and place the blanched green beans on the bottom of the dish evenly. Top with "cream" of mushroom soup. Place in the oven for 20 minutes.
While that is baking, take half of a red onion, remove the outer layer of the onion (if it's still on there) and put in the trash bowl. Slice the onion top to bottom into thin slivers. Once that is done, wipe out the large skillet (or grab a new one if you like washing dishes), place back on the stove and turn on medium heat. Once it's hot, add a tsp of bacon grease (or extra virgin olive oil) and coat the bottom of the pan. Add the onions, use your spatula to attempt to make an even layer then let be for 2-3 minutes to start carmelizing. Stay close by to make sure they don't burn (you'll smell it). After 2-3 minutes, stir to flip them over and let them be again. They won't become crispy but they'll get browned and taste sweet.
After 20 minutes, remove the casserole from the oven and evenly top with caramelized onions. Place back in the oven on the top shelf for another 5 minutes. Remove and serve.