Conchiglie with Tomato & Basil

3 lbs ripe vine tomatoes
16-18 cloves garlic, finely sliced
1/2 cup red onion, chopped
1/3 cup extra virgin olive oil
4 Tbsp unsalted butter
Salt to taste
Black pepper to taste
1/2 cups fresh basil, coarse chopped + leaves for garnish
1/2 cup shredded mozzarella cheese
1 lb medium-size shell pasta
Reggiano cheese to sprinkle

HEAT olive oil and butter in a skillet. Add sliced garlic and onions. Saute over low heat until onions and garlic turn a light golden brown. Add diced tomatoes and cook together with garlic and onions for 5 minutes. Season with salt and pepper to taste. Add chopped basil and stir.
COOK pasta according to package directions and drain.
SERVE pasta in a soup plate or bowl and top with tomato mixture and freshly grated Parmigiano Reggiano cheese. Garnish with fresh basil leaves and shredded mozzarella.