Portobello mushroom sandwich

Name: Portobello mushroom sandwich
Ingredients: 4 portobello mushrooms; 3 garlic cloves, peeled, minced; 2 tbsp olive oil; ½ onion, peeled, finely chopped; 50g breadcrumbs; 1 tbsp fresh parsley; 225g plain cream cheese; 1 tbsp lemon juice; salt and pepper; 1 ciabatta, quartered and sliced in half lengthways