Step 1

In a medium, heavy-based saucepan, heat oil on medium. Saute celery, onion and garlic 4-5 minutes, until tender.

Step 2

Stir in tomatoes and stock. Bring to boil. Reduce heat to medium. Simmer 10 minutes. Stir basil through. Cool slightly. Using a hand blender, puree mixture until smooth.

Step 3

To make white sauce, melt butter on medium in a small saucepan. Add flour and cook, stirring, 1 minute. Remove from heat. Gradually stir in milk, until smooth. Return to heat. Cook, stirring, until mixture boils and thickens. Simmer 3 minutes, stirring. Season to taste.

Step 4

Gradually add tomato puree to white sauce, stirring constantly until smooth. Bring to the boil on medium. Reduce heat to low and simmer 1-2 minutes. Serve topped with extra basil leaves, a drizzle of olive oil and black pepper.