BUTTERED SPINACH, TOMATO & MOZZARELLA TOAST

200g baby plum tomatoes • 2 tbsp extra virgin olive oil, plus extra to serve • 2 tbsp red wine vinegar • 260g spinach • 30g unsalted butter • 4 slices sourdough bread • 1 garlic clove • 1 ball buffalo mozzarella, drained, at room temperature • 80g black olives, pitted and roughly chopped • ½ x 25g pack flat leaf parsley, leaves roughly chopped