Pressed Broccoli Rabe and Mozzarella Sandwiches

Name: Pressed Broccoli Rabe and Mozzarella Sandwiches
Ingredients: 3/4 lb [340 g] broccoli rabe (an average bunch), tough stems discarded, roughly chopped; 3 Tbsp olive oil; Kosher salt; 2 large garlic cloves, minced; Pinch of red pepper flakes; 1/4 cup [40 g] green olives, pitted and finely chopped; 1 1/2 Tbsp drained brined capers, finely chopped; 1 Tbsp red wine vinegar; 4 individual-size sandwich rolls, split (I like rolls with sesame seeds for this, but you do you); 1 lb [455 g] fresh mozzarella cheese, sliced