Cut the tomatoes in half lengthwise. Brush with the oil and sprinkle with salt.
Peel and slice the onion into thick slices. Brush with oil.
Grill the vegetables (on a vegetable rack) over a hot grill until the tomatoes are soft and the onions "crisp-tender." Cool the tomatoes and slip off the peelings.
Chop the tomatoes and onions.
Whisk together the sour cream, cream cheese and mayonnaise until creamy.
Fold in the tomatoes, onions, shredded basil and garlic. Season to taste with salt and
Cover and chill until ready to serve. At serving time garnish with basil sprigs.
Serve with the freshly made corn chips.
Cut each tortilla into 6 triangles.
Heat about 3" of oil in a heavy pot to 365 °F. Fry the tortillas until very crisp, but do not allow to brown. Drain well on paper towels.
Sprinkle lightly with salt.
Makes 72 chips.