In a large skillet, heat 1 TBL of butter over meduim-high heat; add minced garlic and cook 1 minute. Add parsley, shrimp and wine and cook for 2 minutes, stirring constantly, until shrimp turn pink. Do not overcook. Transfer shrimp mixture to small bowl.
In same skillet, heat 3 TBL butter until melted. reduce heat to low and add cream, parmesan and red pepper flakes; cook for 3 minutes, stirring constantly, until cheese melts and sauce is smooth. stir in salt and pepper.
To serve, place warm fettuccine in a serving dish, add shrimp mixture, stiring to combine. Add cream mixture, mix well. Add cubed avocado and toss gentle to coat throughly.