Melt 6 tbs butter in large saucepan and add the carrots, both onions, radishes, parsley, basil, and garlic. Saute the vegetables, stirring often, until they begin to color--about 20 minutes. Cover the saucepan and simmer the vegetables for another 15 minutes.
Add the tomatoes, zucchini, bell pepper, wine, salt, pepper, and sugar. Simmer the sauce, uncovered, for about 45 minutes to 1 hour.
In a small pot, melt 1 tbs butter and stir in the flour. Cook the roux for a few minutes over very low heat, stirring constantly. Heat the cream and stir it into the roux with a whisk. Add the tomato paste and whisk the mixture until it is perfectly smooth. Stir it into the vegetables and wine, along with the grated parmesan cheese.
Continue simmer the sauce over low heat, stirring often, until it is as thick as you want it to be.
Cook the shell pasta (conchiglie) in a large kettle of boiling salted water until they are al dente, drain them completely, and pour them into a large, heated serving dish. Ladle as much of the sauce over them as you like, toss them, and serve immediately, with more grated parmesan cheese.