Peel and dice the celery root into small cubes.

Combine celery root, garlic clove, and coconut milk in a saucepan.

Bring the mixture to a boil, then reduce the heat to low.

Simmer until the celery root is tender, approximately 30 minutes.

Transfer the cooked celery root and liquid to a blender.

Blend until smooth, creating a puree.

Season the puree with salt to taste.

Heat olive oil in a large saucepan.

Add the mushrooms to the saucepan and cook over high heat for 4-5 minutes, until they begin to caramelize.

Add olives, herbs, capers, chopped garlic, red pepper flakes, salt, and black pepper to the mushrooms.

Mix the ingredients well and cook for an additional 1-2 minutes.

Remove the saucepan from the heat.

Drizzle lemon juice over the mushroom mixture.

Serve the mushroom mixture atop the celeriac mash.