01 -
Preheat the oven to 400°F and line a baking sheet with parchment paper.
02 -
In a skillet over medium heat, heat olive oil and sauté the finely chopped cremini mushrooms until browned. Add the baby spinach and cook until wilted. Season with salt and black pepper to taste. Remove from heat and allow to cool.
03 -
Season each chicken breast evenly with salt and black pepper, then coat both sides with Dijon mustard.
04 -
Roll out the thawed puff pastry on a lightly floured surface. Place the cooled mushroom and spinach mixture in the center of each pastry sheet, lay a seasoned chicken breast on top, then fold the pastry edges over to fully enclose the filling. Seal edges carefully.
05 -
Brush the assembled Wellingtons with the beaten egg to promote browning. Arrange on the prepared baking sheet and bake for 30 to 35 minutes, until the pastry is golden and crisp and the chicken is cooked through.
06 -
While the Wellingtons bake, combine heavy cream and low-sodium chicken broth in a saucepan over medium heat. Stir in remaining Dijon mustard and fresh thyme or parsley. Simmer until slightly thickened.
07 -
Slice the baked Wellingtons and drizzle with the warm Dijon cream sauce before serving.