In a large straight sided frying pan over medium-high heat, add olive oil. Add shallots and saute until soft; 1 to 2 minutes.
Add Champagne, lemon juice, and parsley to pan. Bring to a boil and reduce heat to a bare simmer.
Slide fillets into liquid, cover and poach 3 to 4 minutes or until done. Transfer to plate; set aside. DO NOT EMPTY PAN.
Ladle 1/2 cup of poaching liquid into small pot over medium heat. Add cream and bring to a boil. Reduce to a simmer and whisk in white sauce mix. Stirring constantly, simmer 1 minute. Return fish to poaching liquid just to heat through.
Transfer fish to serving plate, spoon over sauce and garnish with lemon and parsley.
For the salad, mix together arugula, tomatoes, corn, and dressing. Garnish with Parmesan shavings.