To prepare pesto, cut bell peppers in half lengthwise; discard seeds and membranes. Place pepper halves, skin sides up, on a foil-lined baking sheet; flatten with hand. Broil 10 minutes or until blackened. Place in a zip-top plastic bag; seal. Let stand 15 minutes. Peel and discard skin.
Combine peppers and next 7 ingredients (through garlic) in a blender or food processor; process until smooth.
To prepare cheese filling, combine cheeses, 1/4 teaspoon salt, and red pepper in a medium bowl; stir well.
Line an 8 x 4-inch loaf pan with plastic wrap, allowing plastic wrap to extend over edges of pan. Spread about 1 cup of cheese mixture in bottom of pan. Spread 1/2 cup pesto over cheese mixture. Repeat procedure with remaining cheese filling and pesto, ending with cheese filling. Cover and refrigerate 6 hours or overnight.
To serve, invert terrine onto a platter; remove plastic wrap. Garnish with additional basil leaves, if desired. Serve with crackers.