For relish, in a food processor, combine olives, raisins and shallot; pulse until coarsely chopped. Add oil and vinegar; pulse until combined but not pureed. Transfer to an airtight container and refrigerate at least 1 hour or up to 2 weeks.

Spread cut side of top of each roll with mayonnaise and bottom with mustard. Place 2 slices each ham, pork and cheese on bottom of each roll, then spread with 2 tbsp relish. Cover with tops of rolls.

In a large skillet, melt butter over medium-low heat. Place 2 sandwiches in skillet and press down using a large flat heatproof object such as a bacon press or the bottom of a heavy skillet. Cook, turning once, until golden brown and cheese is melted through, 12 to 14 minutes. Repeat with remaining 2 sandwiches. Serve immediately. Makes 4 sandwiches.