Heat a non-stick skillet over medium-high heat. Melt butter with olive oil until frothy. Cook trout filets, skin side down, for 2 minutes, then carefully flip with a thin wide spatula. Cook for another minute or until almost cooked through, then add garlic, parsley, and lemon juice and continue to cook for another minute or so until the fish is golden brown and the flesh flakes off easily with a fork. Transfer to serving plates and enjoy.