I have been told that this winter in Denmark was one of the coldest since the second world war. The waters of the rivers and canals outside my restaurant in Copenhagen froze and despite living here all my life that is something I have never seen before. For us at Noma it was a particular problem. The food we cook and serve is Nordic, and a significant number of our ingredients cannot be bought from the store or ordered in. They have to be foraged from the parks, woods and shorelines around the city. But when the snow is deep and the temperatures so low it's not exactly that easy.

Nevertheless we have to keep true to what we are and what we do. It makes sense here in Scandinavia, where picking your own mushrooms is almost a ritual. One season there were so many ceps in the forests around us that you would walk in for an hour and come out with black bin bags full of the things.

So when we came to open Noma, with our commitment to a new style of cooking that turned away from the otherwise terrific classical French repertoire – no olives or its oil, no tomatoes unless briefly in season, no bulb garlic – to something distinctive and regional, it made sense that a lot of our ingredients should be those we could find, not least because they are so available. That's the beauty of Copenhagen. You can just go into its parks and find the likes of wild garlic and yellow star of Bethlehem and march violets, all of which we use in our dishes.

Other things came from further away. I studied recipe books and nature books, learned about wood sorrel and ground elder and particular kinds of seaweed to be plucked from the shore. We also developed a network of professional foragers. We have one man who has been doing it for decades. He is one of those rare characters, with teeth that go in all directions and a book in which he has been keeping notes about the weather and the locations of particular mushrooms since the 1970s. This information he keeps to himself, like it was the recipe for Coke. They are his life, his treasure.

But what is most important to me is that my staff should be out there foraging too. All of the people who work in the kitchen with me go out into the forests and on to the beach. It's a part of their job. If you work with me you will often be starting your day in the forest or on the shore because I believe foraging will shape you as a chef. I know it has shaped me. If you see how a plant grows and you taste it in situ you have a perfect example of how it should taste on the plate. But it's more than that. When you get close to the raw materials and taste them at the moment they let go of the soil, you learn to respect them. We never alter the raw material to such an extent that, when they reach the plate, they no longer have any connection with their origins.

The restaurant industry is brutal. You work your arse off. You worry about bookings and gross profit and larder management. So waking up after way too little sleep and going out into the countryside and eating these wild herbs and experiencing these subtle, brittle flavours forces you to engage with both the world around you as a cook and particularly with the seasons.

This year we have had to be smart and cook with ingredients that we have never tried before: monkfish livers, for example, or cod milt – sperm – which is a traditional Danish ingredient but hasn't previously been a part of our repertoire.

We also had to work with a lot of pickled ingredients. Last year we had picked 100 kilos of wild beach roses, which grow along the shoreline and are a wonderful pink-purple colour. We put them into apple vinegar which helped them to keep their pigment and also enforced their strong rose flavour. Those we have used as herbs on our dishes. We had also pickled elderflowers and axelberry shoots, other shoots of spruce and beech. We dried a lot of blueberries in the autumn, rehydrated them with vinegars, which we often use as a seasoning instead of salt, and then turned that into a purée to go with slow-cooked ox cheeks. All of that gave us something to work with. The restrictions could be frustrating, but also forced us to be more inventive.

But all the time there was only one subject of conversation in the kitchen: when would winter end? Everyone was desperate for that special moment, when they would finally pick up a small bag and a small pair of scissors and go out into the forest or on to the shore where, with too cold fingers, they would at last be able to pick the very first shoots of spring. That, for us, is where the joy of cooking begins.

Noma's vegetable field with soil and herbs

Maltsoil

Day 1

350g flour
85g malt flour
50g hazelnut flour
25g sugar
75ml beer

Day 2

40g flour
20g malt flour
50g hazelnut flour
4g salt; 75g melted butter

Day 1 Mix the ingredients from day 1 and dry for 5 hours at 80C, discarding all the lumps.
Day 2 Mix the ingredients from day 2, add to day 1 and work it briefly ensuring it is homogeneous.

Vegetables (check availability)

4 orange and 4 yellow carrots
4 standard radishes and 3 black, green or red radishes
1 Jerusalem artichoke
1 baby celeriac
4 baby leeks and 4 baby parsley roots

For the butter emulsion:

60ml water
50g butter

Peel the carrots leaving 1cm of the tops and cut in half so you keep top and bottom separately. Scrape the radishes and leeks and halve. Scrape the celeriac and artichoke and quarter. Blanch the vegetables until tender in salted water.

Purée

80g peeled potatoes
5g butter
15g cream
25ml water
Horseradish juice, to serve

Boil the potatoes and crush with a fork. Add the rest of the ingredients while still warm.

Herbs

12 leaves from the tops of the carrots
4 leaves from the parsley roots

Serving

Heat the water, whisk in the butter and heat the vegetables in this butter emulsion. Heat the purée, seasoning it with a bit of horseradish juice. Serve a spoonful on a stone and add the vegetables. Sprinkle maltsoil on top and add the herbs. Serves 4.