Preheat the oven to 150 degrees Celcius.
Season the cod fillets with salt and pepper and put in a oven proof dish. Bake for 15-20 minutes depending on how raw you like them and how thick they are.
Bring water to a boil and boil the cauliflower florets until soft (if using).
When 5 minutes remain for the cod to be finished preheat a nonstick pan over medium heat with some butter (if using).
Sauté the chanterelles with shallots and season with salt and pepper. Fry until golden brown.
When the cauliflower is ready, drain and then mix using a hand mixer until you have a purée.
Add lemon juice, dijon mustard, salt and pepper.
Divide the purée between two plates.
Add cod to the plates and top with fried chanterelles and lingonberries.