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Caramelised Onion & Shallot Tart with Watercress & Pickled Shallot Salad

Updated: Jun 21, 2021

by Rob Howell from Root (Bloomsbury Absolute)

Photography: Alexander J Collins

When I first discovered just how good a well-roasted shallot was, I began using them in everything! And when used in a tart as here they are just wonderful, whilst the onion purée brings a well-rounded sweetness to it all. The spicy leaves of the cress work perfectly with the sweet caramelised onions.



2 shallots, very thinly sliced into rings

pickle liquid (see recipe below)

100g watercress

salad dressing (see recipe below)


6 banana shallots, skin on

75g caster sugar

3 tablespoons cooking oil

1 x 320g sheet of puff pastry beaten egg, to glaze

1 recipe quantity of onion purée (see recipe below)



Preheat the oven to 190°C/170°C fan/Gas Mark 5.

Start the salad . Place the shallot slices in a bowl, sprinkle with a little salt, then add enough pickle liquid to cover. Set aside.

For the tart, trim off the root of the shallots and cut each shallot in half lengthways. Scatter the sugar on to a plate and place the shallots, cut-sides downwards, in the sugar, then transfer them to a clean plate. Set aside.

Heat the cooking oil in a large saucepan over a medium heat.

When hot, carefully add the shallots sugared-sides downwards, and cook gently for about 10–12 minutes, until the shallots have a good amount of caramelisation. Add 100ml of water to the pan; this helps deglaze the pan and cook the onions, and intensifies the flavours.

Cook for another 5 minutes. Using 2 forks, carefully turn over each shallot half, turning them skin-sides downwards. Cook for a further 5 minutes, until the shallot halves have softened slightly, then remove from the heat and leave until cool enough to handle.

Meanwhile, lay out the pastry sheet on a baking tray lined with baking paper (or use the paper the pastry comes rolled in) and brush it all over with the egg glaze. Using a sharp knife, score a 2cm border all around the edge of the pastry. Spread the onion purée evenly over the pastry up to the border.

Once the shallot halves are cool enough to handle, remove their skins and place them tightly on top of the purée to cover the tart base. Bake for 20–25 minutes, until the pastry is crisp and golden brown at the edges. (Adjust the temperature during cooking if it looks as though the tart is baking unevenly.)

While the tart is baking, construct the salad. Place the watercress in a serving bowl and scatter over the pickled shallot rings. Drizzle over the dressing. Serve the tart warm, in slices, with the salad alongside.

Pickle Liquid

We keep the liquid in the restaurant kitchen at all times ready to go. This is our base pickle recipe. You can tailor the pickle as you wish, adding extra flavourings such as citrus peels, spices or aromatics. Make a large amount to keep in the fridge for use as the occasion demands.

Makes about 1 Litre


600ml white wine vinegar

400g caster sugar

300ml white wine

Place the ingredients in a saucepan with 300ml of water. Whisk them together and place them over a medium heat. Bring to the boil, then immediately remove from the heat. Leave the liquid to cool, transfer it to an airtight container and keep refrigerated until you’re ready to use.

Salad Dressing

This is a classic sharp salad dressing that we use with many of our dishes served at Root. Good with vegetables cooked on the grill, for salads, for finishing certain dishes or simply as the mood and the ingredient to hand takes you. Use a good quality vinegar.

Makes about 500ml


75ml chardonnay or other good quality white wine vinegar

1 tablespoon Dijon mustard

200ml cooking oil

50ml rapeseed oil

Put the vinegar into a food processor and add the mustard. With the processor working on full speed, add the oil through the feed tube. Process until the mixture fully emulsifies and the dressing is thick and creamy.

Alternatively, make the dressing in a bowl: whisk the vinegar and mustard together in the bowl and add the oil, whisking all the time. The results will be less emulsified than you get in a food processor – more of a vinaigrette – and the mixture will split once you store it. Just give it a shake or a whisk again to recombine before using.

Burnt Onion Purée

This burnt onion purée is great to use in a variety of dishes, such as risottos, stews, sauces and gravies, having an intensely dark, sweet flavour. The key to success is to cook over a high heat with a good amount of salt – you want that delicious roasted, caramelised onion flavour.

Makes 500g


6 onions, thinly sliced with a mandolin

4 tablespoons cooking oil

200ml white wine, cider, vegetable stock or water

1 tablespoon rapeseed oil

1 tablespoon sherry vinegar

Sea salt

Sprinkle the onion slices with salt. Heat the cooking oil in a large saucepan over a medium heat. When hot, add the onions and cook for about 10-15 minutes, until softened and cooked down and starting to catch on the bottom of the pan. Keep cooking and stirring for a further 5 mins, until the onions have darkened – you want them really caramelised, but not burnt (despite the name!).

Add the white wine, cider, vegetable stock or water and deglaze the pan, scraping up the stickiness from the base. Cook out the liquid until it has all gone (about 10 minutes), leaving you with soft onions.

Transfer the onions to a food processor and blend to a smooth purée. Add the rapeseed oil and vinegar, blend again then taste and season. Transfer to an airtight container & refrigerate until needed.

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