Fry the bacon in a pan over medium-high heat for about 8 minutes until crispy. Drain on paper towels.
Pluck the thyme leaves and chop finely. Core and finely chop the red chilli pepper. Mince the garlic clove and mix with the thyme and chilli. Remove the stems from the portobello mushrooms. Drizzle both sides with 6 tablespoons olive oil, season with salt and pepper, and sprinkle with the garlic-thyme-chilli mixture.
Mix 4 tablespoons mayonnaise with 2 tablespoons lemon juice and 1 teaspoon hot mustard. Season with salt and pepper. Slice the tomato and red onion. Wash the rocket and spin or pat dry. Coarsely grate the 40g parmesan cheese.
Heat a grill pan over medium-high heat. Place the seasoned mushrooms on the grill and cook for 6-8 minutes on each side.
While the mushrooms are grilling, cut the ciabatta rolls in half horizontally. Drizzle the cut surfaces with the remaining 2 tablespoons olive oil. Toast in a preheated 200°C (400°F) oven for about 3 minutes until lightly golden.
Spread the rocket, tomato slices, and onion slices on the bottom halves of the toasted ciabatta. Top with the grilled mushrooms and bacon slices. Sprinkle with the grated parmesan. Spread the mayonnaise mixture on the cut surfaces of the top halves and place on top.