Melt the butter in a frypan over medium heat. Stir in the eschalot; cook and stir until the onion has softened and turned translucent, about 5 minutes. Stir in the mango, honey, 1/4 cup olive oil, white wine, chilli flakes and salt. Reduce heat and simmer until liquid has reduced slightly, about 10 minutes.
Brush both sides of the groper fillets with 1 tablespoon of olive oil and season with salt and white pepper.
Heat a large frypan over medium-high heat. Arrange groper fillets on the frypan and cook until the fish is opaque and separates easily under a fork, about 4 minutes on each side. Serve the fish with the mango sauce on top.