Set the spinach in a strainer over a bowl to defrost and drain ahead of time or defrost in a glass measuring cup in the microwave then set in a strainer to drain.
In a large pot of boiling water cook fettuccine as per package instructions until slightly al dente. Reserve 1/2 cup of the pasta water for the sauce. Rinse pasta under cold water to stop cooking and toss with 1 teaspoon melted butter to ensure that it does not stick together.
In a large frying pan or brasier melt 1 tablespoon of butter and sauté garlic for 1 minute. Mix in pasta water and cream cheese with a whisk until melted and smooth.
Combine chicken broth and flour in a measuring cup and whisk with a fork until flour is dissolved and add to the sauce.
When sauce has thickened turn off the heat and add the cheese stirring until melted and then add the cream, salt and pepper. Taste and season additionally if necessary.
Stir in chicken, spinach, peas, parsley and pasta. Prepare to take your dish home for a quick reheat.
Option: Toast breadcrumbs in a frying pan with a bit of butter and sprinkle as a garnish on served pasta.