Over medium heat, saute onions and garlic in a 1 gallon stock pot. Add diced potatoes and fresh thyme. Cover with stock and simmer until potatoes are soft. Puree with hand blender. Slice leek into thin circles and fold into potato soup and simmer until leeks are soft but still bright green. Finish soup with cream, and salt and pepper.
Cut circles out of four slices of fresh rye bread. Brush with olive oil and toast. Garnish with smoked salmon.
Pour potato leek soup evenly into four soup bowls and garnish with smoked salmon crouton and fresh parsley.