In a small bowl combine the 3 tablespoons of melted butter and cocoa powder. Use a fork and stir just until the cocoa powder is moist. Set aside
In a large mixer bowl combined softened butter, and powdered Swerve. Beat on medium about 1 minute or until creamy
Scrape sides of bowl if needed. Add cocoa/butter mixture and vanilla. Beat on medium about 30 seconds or until fully combined
Scrape sides of bowl if needed. Change paddle attachment to a whisk attachment on standing mixer. Add 2 of the eggs and whisk on medium 5 minutes or until combined and fluffy.
Scrape sides of bowl if needed and add remaining 2 eggs. Whisk on medium another 5 minutes or until fully combined and fluffy.
Scrape sides of bowl again if needed and whisk on medium another 5 minutes or until mixture expands slightly and remains fluffy.
Scrape down sides of bowl one more time if needed and whisk on medium one more time or until fluffy and mixture can hold its own shape.
Remove prepared pie crust from refrigerator. Scoop mixture into pie crust and use a spatula to smooth the filling evenly in the pan. Chill for at least 2 hours or until firm
When ready to serve, top pie with whipped topping/cream and chocolate shavings if desired. You can also slice the pie and place desired amount of whipped topping/cream on individual slices. Store leftovers in the refrigerator