10-12ouncesturkey breastroast or smoked, warmed if desired
For the gravy
Melt the butter in a medium saucepan over medium-high heat.
Add the mushrooms, thyme, salt and pepper. Saute, stirring often, until the mushrooms are soft and turning golden in color, about 5 minutes.
Stir in the flour and cook until it starts to brown, 5-6 minutes.
Add the onion and celery and cook until they start to soften.
Whisk in the chicken broth and Cajun seasoning. Bring to a boil then reduce to a simmer and let simmer until the mixture reduces by half and reaches the desired thickness. Season with more salt and pepper as desired.
For the sandwiches
Toast bread, if desired.
Spread mayonnaise on one side of each slice of bread.
Top bread with turkey.
Divide the gravy between the sandwiches and serve.
To assemble the sandwiches, spread about 1 1/2 teaspoons of the mayonnaise on each slice of bread. Arrange equal amounts of the turkey on top. Ladle equal amounts of the mushroom gravy (almost 1/2 cup each) over each open-faced sandwich. Serve immediately.