Combine sugar, flour, milk and cream in a heavy saucepan. Cook over medium-high heat, stirring constantly, until thick and bubbly. Continue to boil for one minute. Remove from heat.
In a medium bowl, beat the egg yolks. Gradually stir in 1/4 of the hot mixture into yolks. Pour yolks back into remaining hot mixture stirring constantly. Cook, stirring constantly, for 2 minutes. Remove from heat and stir in coconut. Pour into baked pie shell.