Salvadoran Panes con Pollo (Chicken Sandwich)

Ingredients

• 1 whole chicken (about 1.2 kg, cut into serving pieces)
• 2 tbsp vegetable oil
• 1 medium onion (chopped)
• 1 red bell pepper (chopped)
• 3 cloves garlic (minced)
• 3 medium tomatoes (chopped)
• 2 tbsp tomato paste
• 1 tsp ground cumin
• 1 tsp ground achiote (annatto or paprika)
• 1 tsp dried oregano
• 2 bay leaves
• 500 ml chicken stock
• Salt
• freshly ground black pepper
• 4 crusty sandwich rolls (bolillo or baguette-style)
• 1 small cucumber (thinly sliced)
• 1 small tomato (sliced)
• ½ small red onion (thinly sliced)
• 1 small lettuce (leaves separated and washed)
• 2 radishes (thinly sliced)
• 4 tbsp mayonnaise
• 1 tbsp mustard
• 2 tbsp Worcestershire sauce