This savoury custard tart celebrates some of my favourite flavours (and dishes): jammy miso leeks, savoury-sweet chawanmushi (a Japanese steamed custard flavoured with dashi) and toasty sesame seeds, all enveloped in flaky pastry. It feels decadent, so it’s best served with a simple fennel salad, zingy with apple cider vinegar and mustard. It’s excellent eaten while still warm from the oven (be patient!), but even better as leftovers, because I have a soft spot for cold eggy tarts.

Caramelised miso leek custard tart with apple cider vinegar fennel slaw

Shop-bought pastry can, of course, be used, but making it from scratch is what makes this dish that much more special.

Prep** 30 min**** Chill 1 hr 15 min+ Cook 45 min** Serves** 6-8**

For the pastry 185g plain flour, plus extra for dusting **1 **tsp salt 100g cold unsalted butter, cubed

For the leeks **2 ****tbsp vegetable oil ** 350g leeks, trimmed, halved lengthways and cut into 3cm segments **Salt 2 **tbsp red miso **2 **tbsp honey

For the egg mixture **5 eggs 150ml whole milk 1 ****tbsp dashi granules 1 **tbsp sesame seeds Chives, thinly sliced, to garnish Chilli oil, for serving

For the slaw 300g fennel, trimmed and thinly sliced or cut using a mandoline 2 sprigs fresh flat-leaf parsley, tender stems and leaves chopped **2 ****tbsp apple cider vinegar 1 **tsp dijon mustard

First make the pastry: in a food processor, blitz the flour, salt and butter into a breadcrumb-like consistency. With the motor on pulse, slowly add 65ml cold water, until a rough ball of dough forms. (Alternatively, sift the dry ingredients into a mixing bowl and rub in the cubed butter. Add the water slowly and mix gently to make a dough.) Wrap the dough in clingfilm or baking paper and chill for at least an hour.

Put the vegetable oil in a pan on a medium heat and cook the leeks with a small pinch of salt for seven to 10 minutes, until fully cooked and starting to brown.

In a small bowl, dissolve the miso and honey in two tablespoons of cold water, then pour over the cooked leeks. Reduce for a few minutes on a low heat, until the leeks are jammy and most of the liquid has evaporated, then set aside.

On a floured surface, roll the pastry into a disc to fit a 20cm round loose-bottomed tin. Lay in the pastry, pressing it into the tin, then prick the base with a fork. Return to the fridge for 15 minutes.

Heat the oven to 220C (200C fan)/425F/gas 7 and put a baking sheet inside to heat up. Line the chilled pastry shell with baking paper and weigh it down with baking beans. Blind bake for 15 minutes, then remove the beans and paper, and bake for five minutes more, until lightly brown. Remove and trim any overhanging pastry, and turn down the oven to 200C (180C fan)/390F/gas 6.

In a bowl, whisk the eggs, milk and dashi granules. Spoon the cooked leeks into the pastry shell, then pour in the egg mix. Bake for five to seven minutes, until the custard is slightly set. Sprinkle the sesame seeds on top and bake for another 20-25 minutes, until the pastry is golden and the sesame seeds toasted. Cool to room temperature.

Meanwhile, make the slaw by gently massaging the sliced fennel with the remaining ingredients, then season to taste.

To serve, slice and garnish the tart with chives. then serve with the slaw and the chilli oil.

Ferment: Simple Ferments and Pickles, and How to Eat Them, by Kenji Morimoto, is published by Pan Macmillan at £22. To order a copy for £19.80, visit the guardianbookshop.com