Bring a quart of stock to boil on the stove in a large soup pot.
Add chopped celeriac, potatoes, and apples. Simmer on a low boil for about 20 minutes until very soft when smashed with a spoon. Remove from heat.
MEANWHILE, heat up a pan with oil. Saute sliced onions and shallots on medium high with a lid for a couple of minutes, then remove the lid.
Add garlic and a pinch of salt & pepper. Saute together until all are translucent and browned. Add this onion mixture into the soup pot with the root veggies.
Use an immersion blender to blend the soup to a smooth consistency (or transfer to blender and carefully blend in small batches). Stir in coconut milk.
In your frying pan that's still hot from the onions, toss in your bread cubes and toast with a couple good splashes of oil and some salt and pepper. Add hazelnuts when the bread is almost toasted, so they finish at the same time. Remove from heat.
Serve soup topped with shredded cheese, hazelnut crunchies, and finely sliced apples.