Cook lentils in water.
Drain and blend or process until a purée is obtained.
In a medium size pan brown bacon until golden.
Remove and in the same fat add butter, onion, garlic, salt, pepper, tomato paste, and chicken broth. Add lentils and continue cooking, mixing well after each addition.
Dissolve flour in ¼ cup of the water. Incorporate to preparation together with rest of water.
Bring to a boil and continue cooking a few minutes more.
Serve in soup bowls and garnish with cooked lentils or bread croutons and sprinkle parsley on top.