In a saucepan over medium heat, melt butter, stir in flour and cook for a few minutes until golden. Add milk and cream, bring to a gentle simmer and continue to stir until thickened. Add pesto, parsley, garlic, Parmesan cheese, salt, pepper, Worcestershire and Tabasco; stir until well blended. Reduce heat to the lowest setting and keep warm, stirring occasionally. Cook pasta quickly in a large pot of boiling water (3 to 4 minutes, or until al dente). At the same time, poach the pepper strips, snow peas and shrimp in another pot in a small amount of boiling water. Cook for about 3 minutes, or until vegetables are just tender and shrimp is cooked. Drain the pasta, mix it with the sauce and divide among four individual serving bowls. Garnish each evenly with hot cooked shrimp, pepper strips, and snow peas; serve immediately.