Preheat the oven to 400.

Wash, dry and break up the cauliflower into pieces. A knife may be required, especially to cut away the stem + leaves, but do not worry about a consistent size for these florets. Toss the cauliflower with olive oil, a pinch of salt, spread on a baking sheet and place in the oven.

Cut off the top tip of the head of garlic. Wrap in a bit of foil, or leave it free and toss onto the same pan as the roasting cauliflower.

Cut the onion in half. Trim off the ends and then cut into strips from end to end. Toss the onion strips with the flour and a generous pinch of salt in a bowl. Drizzle olive oil all over a baking sheet. Shake the excess flour off of the onion strips, separate the onions and spread out on the baking sheet. Roast the onion strips. Check these every 5 minutes as they can go from white to burnt quickly. Toss periodically as most of the color will occur where the onions are touching the pan.

Next, place the green beans in the casserole dish with a generous splash of water (about 1/4 cup approximately) and cover with a lid or foil. Place in the oven for about 10-20 minutes until they are as tender to the bite as you like. You will be baking them again with the sauce, but oven-steaming them will get the texture closer to a more traditional green bean casserole.

Meanwhile, place the almonds and water in a high-power blender or food processor. Blend until the liquid is smooth and thick without any chunks.

While everything is baking, slice up the mushrooms, saute in a skillet with a generous splash of olive oil. Sprinkle with salt and pepper as well.

The garlic will probably finish first, when the tips are golden and a knife pierces into the cloves easily. Remove it from the oven and place in the fridge to cool enough to handle.

When the cauliflower is tender and soft, place the florets in the blender/food processor with the liquid almonds. Squeeze the roasted garlic out of their skins and add them in as well. Blend until the sauce is creamy + smooth.

Keep a close eye on the onions and remove when ready. When the green beans are the right texture, strain off any excess water and pour on the cauliflower sauce and toss to combine. Top with the cooked mushrooms. Cover it with foil and finish baking for about 15-20 minutes. Alternatively, make this dish to this point in advance, chill in the fridge and then bake for about 40-55 minutes until hot to the touch in the center.

Once the dish is hot and steamy, remove the foil and sprinkle on the crispy onions, bake another 5 minutes and then serve.