Hungarian Mushroom Soup (Gombaleves)

Ingredients:

• 400 g (14 oz) mushrooms, sliced
• 1 small onion, finely chopped
• 2 tbsp butter or oil
• 1 tsp paprika
• 1 tbsp flour
• 750 ml (3 cups) vegetable or chicken broth
• 100 ml (½ cup) milk
• 100 ml (½ cup) sour cream
• 1 tsp dried dill (or fresh, chopped)
• 1 tbsp soy sauce (optional, for depth)
• Salt and pepper to taste
• 1 tsp lemon juice (optional)