- In a large pot, bring 1 cup (250 ml) of the water to a boil with the salt and brown sugar. Stir just until the brown sugar has dissolved. Remove from the heat. Add the remaining water. Place the turkey breast in the brine. Place a plate over the turkey to hold it down and to keep it completely submerged in the brine. Refrigerate for 8 hours.
- Meanwhile, in another large pot over medium heat, cook the onions in 2 tbsp (30 ml) of the oil, stirring often with a wooden spoon and scraping the bottom of the pot, until nicely caramelized, about 20 minutes. Add the spinach and cook for 1 minute or until wilted. Remove from the heat. Add the cranberries. Season with salt and pepper. Mix well. Transfer to a bowl and let cool. Cover and refrigerate for 30 minutes.
- With the rack in the middle position, preheat the oven to 375°F (190°C).
- Drain the turkey and pat very dry. On a work surface, cut the breast in half horizontally without going all the way through to the other side, and open it like a book. Using your hands, lightly press the breast into a rectangular shape as much as possible. Place the turkey, cut side down, on the work surface. Season with salt and pepper.
- Spread the caramelized onion mixture over the entire surface of the turkey breast. Starting with one of the short sides, roll the turkey breast up. Brush with the remaining oil and tightly wrap in a large piece of foil to form a cylinder. Place on a baking sheet lined with parchment paper (see note).
- Bake for 50 minutes or until a thermometer inserted in the centre of the roast reads 165°F (74°C). Do not open the foil. Let cool. Refrigerate for 2 hours 30 minutes or until completely chilled.
- In a small bowl, whisk the egg and milk with a fork. Set the egg wash aside.
- Remove the foil from the turkey roast.
- On a floured work surface, roll the puff pastry into a 13-inch (33 cm) square. Place the turkey, rounded side down, in the centre of the pastry.
- Using a pastry brush, cover the remaining surface of the pastry with egg wash. Fold the pastry around the turkey to cover it completely, cutting any excess dough as needed. Seal the dough at both ends. Tightly roll the Wellington in three layers of plastic wrap. Refrigerate for 1 hour. Set the remaining egg wash aside.
- With the rack in the middle position, preheat the oven to 425°F (220°C). Line a baking sheet with parchment paper.
- Remove the plastic wrap and place the turkey Wellington on the baking sheet, seam-side down. Brush with the egg wash. With the tip of a sharp knife, make thin, shallow incisions along the top of the dough, keeping them close together and not going all the way through. Bake for 35 to 40 minutes or until the dough is cooked and golden. Let rest for 10 minutes.
- Meanwhile, in a large skillet over medium heat, soften the shallots in 2 tbsp of the butter. Add the mushrooms and cook until browned. Add the remaining butter and the flour. Continue to cook until the mushrooms are nicely coated in the mixture, about 2 minutes. Add the broth. Bring to a boil. Let reduce until the sauce thickens. Add the cream. Remove from the heat.
- In a blender, purée the sauce until smooth. Season with salt and pepper.
- On a work surface, slice the turkey Wellington. Serve with the mushroom sauce. Serve with our roasted potatoes with confit garlic and rosemary and balsamic-glazed carrots.
If you buy a turkey breast with skin, you can simply remove it and use it to prepare our crispy turkey skin recipe, which is great sprinkled over our roasted potatoes with confit garlic and rosemary.
We highly recommend using parchment paper because cooking juices will accumulate on the baking sheet as the turkey cooks. The parchment paper will make clean up much easier.