Peel the celeriac and cut into thin sticks. Transfer to a large saucepan.
In another saucepan, heat 1 teaspoon of rapeseed oil over medium heat. Add the garlic and sauté for 2 minutes, stirring constantly. Pour in the broth and bring to a boil. Pour the broth mixture over the celery sticks in the large saucepan, bring to a boil, cover, and simmer over low heat for 25 minutes.
Preheat the broiler to medium-high heat, approximately 220°C (425°F).
Drain the celery and transfer to an ovenproof dish. Brush with the remaining 1 teaspoon of rapeseed oil, sprinkle with parmesan, almond sticks, and black pepper. Top with a few flakes of butter.
Broil for 2 to 3 minutes, until the almonds are golden brown.