Preheat oven to 400 degrees Fahrenheit. 

Trim the cauliflower, removing the outer leaves, and cut the stem so the cauliflower sets flat, do not break the cauliflower apart.

Place the whole cauliflower in a pot large enough to hold the cauliflower and the liquid. Add the stock, thyme ( you can just toss in the whole sprig as it will be remove after cooking), bay leaves, peppercorns, and milk. Adding milk keeps the cauliflower white. Bring to a boil and reduce heat and simmer for about 12 minutes.

While the cauliflower cooks make the beer cheese sauce. In a medium sauce pan bring the beer to a simmer, add the cream and cheddar cheese. Whisk continually until both cheese are melted and smooth. Set aside.

Transfer the cauliflower head to a cast iron skillet, removing the thyme, bay leaves, and peppercorn.  

Pour the beer cheese sauce over the cauliflower and sprinkle 1/2 cup shredded cheddar cheese on top. Place in preheat oven for 10-15 minutes or until the shredded cheese is melted and beginning to brown.

Remove from oven and top with bacon and green onions. 

Cut into wedges and serve with sour cream, remaining 1/2 cup shredded cheese, extra, bacon, and green onions.