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, salt, pepper, worcestershire and tabasco, and stir until blended. Reduce heat 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, snowpeas and shrimp in another pot of boiling water ( 2 or 3 minutes, or until just heated through). Drain the pasta, mix it with the sauce and portion it into heated individual serving bowls. Garnish each portion with shrimp and vegetables, and serve immediately.