Note: while there are multiple steps to this recipe, the instructions are broken down into workable categories to help you better plan for preparation and cooking.

Make the Filling

1. Gather the ingredients. Heat the oven to 400 F/200 C. Grease a heavy baking sheet with butter or line with parchment paper.

2. Bring a small saucepan of water to a rapid boil. Lower the heat slightly and add the farro. Simmer for 10 minutes. Drain and spread the cooked farro on paper towels to dry slightly.

3. Heat the milk until hot, but not boiling. Add 2/3 of the tarragon leaves, stir, and remove from the heat. Set aside to let the flavors infuse.

4. Add the butternut squash and sweet potato cubes to a roasting tray. Toss with 4 tablespoons of the oil and season with salt and pepper. Roast in the center of the oven for 20 minutes. Once cooked, scoop onto clean paper towels to drain.

5. Remove the stalks (reserving) from the portobello mushrooms. Cut the mushroom caps into 1/2-inch thick slices.

6. Heat half the butter in a large frying pan until foaming. Add the mushroom slices and cook for 3 minutes on each side. Let drain on the paper towels with the roasted veggies. Into the same pan, add the shallot and the remaining tablespoon of oil and cook for 6 minutes until soft. Scoop the shallot out with a slotted spoon and add to the paper towels.

7. Add the baby kale to the frying pan and cook for 2 minutes to soften slightly. Add to the paper towels.

8. Into a saucepan, add the remaining butter and melt over medium heat. Add the flour and stir with a wooden spoon to create a thick paste. Strain the infused milk into the pan and whisk furiously until you have a smooth thick cream sauce. Cook for a further two minutes.

9. Finely chop the mushroom stalks then add to the cream sauce and stir. Add the farro and the shallot and stir again. Season with salt and pepper and let cool.

Assemble the Wellington and Make the Sauce

1. Once the sauce is cooled, remove the pastry sheets from its packaging and carefully unroll. Cut the sheets into four rectangles 17 1/2 cm x 11 1/2 cm and lay two pieces onto the baking tray.

2. With the narrow end of the rectangle in front of you, lay the baby kale on the pastry leaving a 1-inch margin around the edge. Spoon a thick layer of the mushroom and farro cream on top. Tuck the buttery slices of mushroom upright into the thick sauce cream working from front to back; do not worry if there are gaps.

3. Carefully place the butternut squash and sweet potato dice on and around the mushroom, filling any gaps to help support the mushrooms to stay upright. Pile any leftover farro cream on top.

4. Brush the margin of the pastry with a little beaten egg. Gently lay the second sheet of pastry over the top, carefully stretching it a little to enclose the filling. Use your hands to mold the pastry around the mixture into a log shape. Press the two edges together, making sure you have an approximate 2 1/2 cm rim all the way around.

5. Use the back of a fork press into the rim to make a tight seal. Trim to create a neat edge at least 2 cm deep (you can use the cut bits of pastry to make decorative leaves). This edge can be crimped as in the image of the recipe or left plain.

6. Brush the puff pastry with a generous coat of beaten egg using a pastry brush. If you are decorating with leaves, cut them out and lay on the top. Using a sharp knife, score the pastry 4 or 5 times making sure not to cut right through. If you are not decorating, score a criss-cross pattern instead. Scoring allows the pastry to breathe and release steam while cooking. Repeat to create the second Wellington.

7. Put the Wellingtons, uncovered, into the fridge to chill and rest for at least 2 hours. If you want to leave it overnight, loosely with parchment or waxed paper.

8. Cook the Wellingtons in the center of the oven for 40 minutes or until golden brown and well risen. Leave to rest for 10 minutes before cutting into thick slices.
9. While the Wellington rests, finely chop the remaining tarragon leaves. Reheat the pan you cooked the mushrooms and kale in over medium heat. Once hot, add the cream and the remaining tarragon. Stir and let the sauce bubble and reduce by a third. Serve warm with the Wellington.

Tips for the Perfect Wellington

• The key to creating a light, crisp Wellington is to make sure all your ingredients are cold when assembling and that they have been dried carefully before assembly.
• At each step of the way the filling ingredients are cooked and drained on paper towels. Don’t skip these steps, since they help prevent a soggy bottom.
• Rest the Wellington once assembled for at least a couple of hours. This gives it time to settle and the pastry to relax.