Bring a large pot of lightly salted water to a boil. Add linguini and cook until tender, about 7 minutes. Drain.
Meanwhile, heat 2 tablespoons butter in a large skillet over medium-high heat. Add mushrooms; cook and stir until tender. Transfer to a plate.
In the same pan, melt 1/2 cup butter with the minced garlic. Stir in the cream cheese, breaking it up with a spoon as it melts. Stir in the parsley and basil. Simmer for 5 minutes. Mix in boiling water until sauce is smooth. Stir in cooked shrimp and mushrooms; heat sauce through.