Set oven to 450°F. Roast garlic head by slicing off top so that all cloves are just visible. Baste with 1 Tbsp of olive oil, wrap with foil and place on a baking sheet. Roast for approximately 45 min. until cloves are soft. After the garlic has cooled off squeeze or scoop the cloves out and save in a small bowl.
In a food processor pulse the peanuts to the coarsely shopped stage. Remove ¼ C. then process the rest for a few minutes until it becomes peanut butter.
Heat the remaining 1 Tbsp of olive oil in a large pot. Add the onions and cook til translucent. Add sliced celery, roasted garlic and honey. Cook at medium heat until the celery is soft, stirring often and being careful not to let it burn. Add the chicken broth and bay leaf and bring to a boil. Add the potato and simmer about 20 minutes until the potato is soft. Remove from the heat and remove the bay leaf.
Purée the soup in a blender or with an immersion mixer, adding the peanut butter at the end. Add the yogurt, blend once more.
Pour into bowls and garnish with the ¼ C. chopped peanuts and celery leaves.