Bring 4 quarts water to a boil in a large saucepan.
Add pasta; cook 7 minutes.
Add shrimp to pan; cook 3 minutes or until shrimp are done and pasta is al dente.
Drain; keep warm.
While pasta cooks, heat a small nonstick skillet over medium heat.
Add nuts to pan; cook 2 minutes or until lightly browned.
Combine 1/2 cup milk and flour in a large saucepan, stirring with a whisk until well blended.
Place pan over medium heat; gradually stir in remaining 1/2 cup milk. Stir in mustard and nutmeg. Bring to a boil; reduce heat to medium-low, and cook 5 minutes or until mixture begins to thicken, stirring constantly. Stir in salt and pepper; cook 1 minute.
Add drained pasta mixture, cheese, and chopped basil, tossing gently to combine.