Heat olive oil and butter in saucepan. Add tarragon, carrot and onion, cover and simmer over very low heat for 5 minutes or until tender. If vegetables are too dry, add a tablespoonful of white wine, cover and cook. When vegetables are tender, remove the cover, add remaining wine, and saffron and evaporate until almost all of the wine is gone. Add the broth, fish stock and diced tomatoes and bring to a simmer. Add the pasta and cook uncovered for 5 minutes or until just tender. Add the shrimp and peas and bring back to a simmer. Season to taste with salt and pepper and garnish with chives or scallions.