Coronation Creation Chicken Sandwich

Ingredients

• 1/2 cup vegetable oil
• 1 tsp tarragon
• 1/2 tsp grainy mustard
• 1/3 cup peach & orange purée
• 1/4 cup lemon juice
• 1 tsp salt
• 1 tsp black pepper
• 1 cup mayonnaise
• 2 tbsp prepared horseradish
• 6 chicken breasts, 5 oz
• 1 head Romaine lettuce
• or
• 1 head leaf lettuce
• 6 sesame buns
• dill pickles, thinly sliced, for garnish