Brush chicken evenly with curry paste and season with 1/4 tsp (1 mL) salt. Transfer chicken to a parchment paper-lined baking sheet and bake at 400°F (200°C) for 12 to 15 min. or until just cooked through. Let chicken rest for 5 min. before slicing.
Meanwhile, spread mango chutney on 4 bread slices and top with spinach and a Swiss cheese. Top with sliced chicken and cap with remaining bread slices. Spread outside of each sandwich with 1 tbsp (15 mL) butter. Bake sandwiches on baking sheet for 8 to 10 min. or until cheese melts and bread is lightly golden brown.
Meanwhile, heat remaining butter in large non-stick skillet over medium heat. Add eggs and fry for 2 to 3 min. for sunny-side up or to preferred level of doneness. Place a fried egg over top of each sandwich and season with salt and pepper. Serve with additional mango chutney, if desired.