In large dutch oven heat 1 tbsp olive oil, 1 tbsp butter.
Add onion, leek and celery, garlic sauté until soft.
Add ham, cook until ham is heated.
Melt in additional tbsp. of butter, then sprinkle flour over ham/onion mixture, sautéing until combined, 1-2 minutes.
Stir in chicken stock, milk and potatoes.
Add bay leaf and pepper.
Continue to simmer, until potatoes are tender about 30-40 minutes. Do not allow to boil.