In the top of a double boiler, combine cream cheese and butter. Heat to melting, stirring occasionally. Add garlic and whisk mixture until blended. Whisk in evaporated milk, pepper, and salt until blended. Stir in 1/2 cup Parmesan cheese and set aside. Cook fettuccine in salted water according to package directions. During the last two minutes of cooking, add peas to boiling pasta water in pot. Drain fettuccine and peas; toss with reserved sauce. Add half the salmon and pecans, mixing gently. Serve immediately, topping each portion with a sprinkling of remaining salmon and pecans mixture.