Combine the evaporated milk, sugar, egg yolk, butter and vanilla in a small saucepan. Bring the mixture to a simmer over medium-heat, stirring frequently. Simmer for 8-10 minutes, or until the mixture has thickened and turned a caramel color. Be careful not to burn.
Remove from heat and stir in coconut and pecans. Allow the frosting to cool slightly and thicken.
Spread frosting on cooled cake, brownies or cookies. Drizzle with semisweet chocolate if desired.
Roasting pecans: To bring out the pecan flavor you can roast them beforehand. Simply bake in the oven at 350°F for 3-5 minutes or until lightly toasted. Storage: Store in a covered container in the refrigerator for up to 5 days. Let sit at room temperature to soften before frosting.