Saute the shallots and garlic in olive oil until translucent but not browned.
Add the tomatoes, white wine, salt, pepper, and sugar. Bring the mixture to a boil, lower it to a simmer, and cook the tomatoes for 20-30 minutes. In batches, transfer the sauce to a blender and purEe until smooth. Strain the tomato coulis through a fine sieve, and if needed, finish the sauce with a pat or two of butter.