Boil linguine in salted water until al dente, then drain. (This can be done while you're making your cajun cream sauce.)
In a large saucepan, melt butter over medium heat.
Add shallot, garlic, cajun seasonings. Stir for about one minute.
Add white wine, and cook for 3-4 minutes, stirring occasionally.
Add lemon juice, cook for one minute (stir a time or two).
Slowly stir in the heavy cream, then the half and half. Allow both to cook in for about 4-5 minutes, stirring occasionally. Turn heat to low, and allow to thicken for 1-2 minutes.
Remove from heat. Grate in the parmesan, and mix in thoroughly. Add pepper to taste.
Add cooked linguine, and toss to coat. Garnish with thinly diced green onion.
If you want a LOT of cream sauce, use 1/2 cup each of half and half and heavy cream, rather than 1/3 cup. Cajun seasoning typically has enough salt in it, so I recommend only adding pepper to taste at the end!