Belgian Tomates aux Crevettes (Tomatoes with Shrimp)

Ingredients

• 4 large ripe tomatoes (firm but slightly soft to the touch)
• 250 g 9 oz North Sea shrimp (or small brown shrimp)
• 4 tbsp mayonnaise (preferably homemade or high quality)
• 1 tbsp Dijon mustard
• 1 tbsp lemon juice
• 1 tbsp finely chopped fresh parsley
• 1 small shallot (finely minced)
• Salt and white pepper (to taste)
• 1 tbsp heavy cream (optional, for a smoother texture)
• 4 leaves of crisp lettuce (for serving)
• 4 slices of baguette or country bread (optional, for serving)
• Extra parsley for garnish