Rinse the green beans and cook for about 10 minutes in boiling salted water. Remove, shock under cold water and drain well. Peel the onion, chop finely and sauté in butter. Rinse the spinach well, add to the onions and cook for 5 minutes until almost all of the liquid has evaporated. Placee the beans and spinach in a blender with the creme fraiche and blend together. Season with salt and pepper.
Soak the gelatin in cold water. Peel the carrots and cook for about 12 minutes in boiling salted water. Dissolve the gelatin in a little of the carrot cooking water, then mix with the vegetable puree. Rinse a loaf pan of 1 liter (approximately 4 cups) depth under cold water and pour half of the vegetable puree in it. Lay the carrots in the pan lengthwise and cover with the remaining vegetable puree. Chill in the fridge at least 4 hours.
For the sauce, scald the tomatoes under hot water, rinse under cold water, quarter, remove the seeds and chop. Season with salt, pepper, herbs and Tabasco.
Before serving the terrine, place the loaf pan briefly in hot water, then turn out onto a plate.