Cut cauliflower into individual florets, each about the same size, wash and dry off.
Peel celeriac and cut into equal 1” x 1” inch cubes.
Remove outer layer of skin off the garlic head, so that only the individual outer skin remains.
Clean shallots and leave whole.
Steam cauliflower so that it is ‘mushy’ – more than just andante. Remove from heat (do not place them into an ice bath – it will make the cauliflower too watery).
In a reasonable-sized roasting pan, place the celeriac cubes and the shallots. Spray with non-stick spray and toss with a small amount of sea salt.
Place the garlic into a small ramekin (big enough to just hold the garlic). Add about 2-3 tablespoons of Low Sodium Chicken Stock (or vegetable stock), cover with foil wrap. Put the ramekin in the corner of the roasting pan.
Place roasting pan in the hot oven, and roast the vegetables until they are soft, being careful not to brown the edges too much (this would ruin the ‘mashed potato’ look).
When the celeriac is soft enough for a fork to easily pierce, pour about ¼ cup of Low Sodium Chicken stock into the roasting pan. Allow it to evaporate (this step will soften the celeriac for blending).
The celeriac and shallots will be done a bit sooner than the garlic, remove from pan and continue to poach the garlic.
Place the celeriac and the shallots into a large bowl, add the cauliflower 2-4 florets at a time and purée with an immersion blender. The cauliflower will add enough moisture to the mash, but if you find it dry, add a little LS chicken stock (very little). The trick to this dish is to not make soup, but a creamy mash.
When you have puréed the celeriac, shallots and cauliflower, add the poached garlic cloves (all of them) and drizzle the LS chicken stock remaining in the ramekin into the mix. Purée until you have a creamy paste. Using a soup ladle, push this mash through a fine sieve (this is important so that the mash is creamy and not chunky or woody).