Pat the Mahi Mahi fillets completely dry with paper towels. This is crucial for achieving a good sear. Season generously on both sides with salt and pepper.
Heat the olive oil in a non-stick skillet over medium-high heat until shimmering. Carefully place the Mahi Mahi fillets into the hot skillet, presentation side down.
Sear for 3-4 minutes until a golden-brown crust forms. Flip the fillets using a fish spatula and cook for another 3-4 minutes, or until the fish is opaque and flakes easily with a fork. Remove the fish from the skillet and set aside on a plate.
Reduce the heat to medium. Add the butter to the same skillet. Once melted, add the minced garlic and sauté for about 1 minute until fragrant, being careful not to burn it. If using, add a pinch of red pepper flakes.
Pour in the white wine and lemon juice. Let it simmer and reduce slightly for about 2 minutes, scraping up any browned bits from the bottom of the pan.
Stir in the chopped fresh parsley. Season the sauce with a little more salt and pepper if needed.
Return the Mahi Mahi fillets to the skillet, spooning the garlic butter sauce over the top. Let them warm through for about 30 seconds.
Serve immediately, drizzled with extra sauce from the pan.