Green Bell Pepper Soup

2 tablespoons [30 g] butter 1 medium-size green bell pepper, seeded and chopped 1/2 small onion, chopped 1 [10 1/2-ounce / 300-mL] can cream of celery soup concentrate 1 [10 1/2-ounce / 300-mL] can milk	Soften together chopped sweet green pepper and onion into melted butter, for 5 minutes. Puree into an electric blender. Transfer into a saucepan. Pour in cream of celery soup and milk. Mix for a few seconds, until smooth. Heat over low heat and serve.