It easier to peel the skins off chorizo if you first soak the whole sausage for a few minutes in a complete covering of boiling water. Once the skin’s removed, cut the sausage into inch-long chunks — they’re heading for your food processor in a minute or two.

Melt the butter in a good-sized skillet over a medium heat. As soon as it starts foaming, add the finely chopped onion and drop the heat to low. You want to let the onion fry gently — and I mean gently — for about 7 minutes, so that it turns translucently soft. Do not let it take on any color — you’re aiming to soften the onions, not to brown them. Good.

Now stir in the chopped mushrooms and let them slowly fry with the onions for another 5 minutes with the occasional good stir. Turn off the heat, and let the mix sit in the skillet. Time now for the food processor.

Tip the chunks of chorizo into your processor and give them a thorough blitzing until you get a consistency similar to fairly coarse breadcrumbs. Now add the onions, mushrooms and all the melted butter from your skillet. Blitz again until the onions and mushrooms are completely combined with the ground chorizo.

Return your skillet to a low heat and add all the chorizo mix. Stir well and let it cook on that low heat for 5 minutes with a few stirs. This very gentle frying will melt most of the full-flavor fat from the chorizo. Turn off the heat, stir in the lemon juice, and tip all the paté mixture into a bowl.

Return the skillet to a medium-high heat and add a level tablespoon butter. Once it foams, add the pork loin, and fry it for 3 minutes or so until its surface gets a pale golden color all over it. Turn off the heat and set the loin aside on a plate. Good.

Assembling/Preparing your Wellington for the oven

Heat your oven to 425F / 220C and set a baking tray — lined with greaseproof paper — in the middle of the oven. That paper’s important because it will prevent the bottom of your Wellington from sticking to the tray.

Beat the egg together with two teaspoons cold water.

While the oven’s heating — and your lightly browned loin is cooling — dust a little flour onto a cold work surface, and lay on it one flat sheet of your defrosted puff pastry.

Now spoon an even, 1/3-inch thick layer of the chorizo paté down the centre of the pastry sheet. Take care that this central layer is about ½ inch wider all round than the size of the pork loin. Good.

Now gently sit the loin on top of the layer of paté. If there’s any juices from the loin left on the plate, mix these quickly into the rest of the paté.

Using your fingers, cover the top and sides of the loin with paté. You’ll find it has enough body so that you can easily coat the surfaces of the loin with an even covering that’s about 1/3 inch thick all over. Good. Almost done.

Now brush a third of the beaten egg mix over all the exposed areas of the pastry sheet.

Take the other sheet of pastry and lay it over the loin. Use your fingers to gently press the edges of the top sheet onto the edges of the bottom sheet — be gentle here but make sure you get a good seal that’s at least ½ inch wide all round the two sheets of pastry. If you think it’s needed, use a sharp knife to cut away any pastry that extends beyond that ½ inch seal. Time for baking.

Quickly brush the top pastry sheet all over with the rest of the egg mixture and carefully transfer the Wellington to the paper-lined baking tray. After 10 minutes’ baking at 400F / 220C, turn the oven down to 375F / 190C.

Bake the Wellington at that lower heat for another 25 minutes. Done. Turn off the heat and remove the Wellington to a carving / cutting board, and let it cool there a little while you cook the spinach.

First, thoroughly drain the spinach in a big colander so that you remove as much water as you can.

Melt the butter on medium heat in a saucepan that’s big enough to hold all the spinach. As the butter foams, stir in the garlic and the salt, and drop the heat to low. You’re aiming here just to soften the garlic and allow it’s flavor to infuse the butter — about 4 minutes on that low heat is all it needs. Make sure the garlic doesn’t start to pick up any color — a few watchful stirs helps with this.

Now add all the spinach to the pan and stir it so that it mixes really well with all the garlicky butter in the bottom of the pan. Cover the pan and let is gently cook on that low heat for 3 minutes with a few stirs. That’s it, spinach done.

Use a slotted spoon to transfer the garlic and spinach — and as little of its juice as possible — to a warmed dish ready for serving.

This is easy with a really sharp carving knife — one that will cut through the pork loin with just a few firm, even strokes.

You want to carve the Wellington into slices no more than ½-inch thick. As you carve each slice, make sure that it doesn’t fall away sideways from the rest of the Wellington — try to keep the entire slice upright. Then hold a broad spatula flat against its outer edge, and carefully transfer it in one whole piece to a diner’s plate.

Once your suitably-impressed guests have stopped praising you, they can then help themselves to the lovely garlicky spinach.