Melt butter in a saucepan over medium heat. Add garlic and celery; cook and stir until softened, 4 to 5 minutes. Pour in chicken stock, increase heat to medium-high and bring to a simmer. Stir in almond butter until dissolved and season with mace. Reduce heat to medium-low, cover and simmer until the celery is tender, 30 to 40 minutes.
Once the celery is tender, turn off heat and allow the soup to stand covered for 1 hour.
Carefully puree the warm soup until smooth using a liquidiser; pour through a sieve into a clean saucepan. Stir in cream and place over medium-low heat. Heat until hot, being careful not to bring to the boil or else the cream will curdle. Season with salt to taste; serve garnished with toasted almonds.