Black jeans are the most useful thing in my wardrobe for evenings. They look sharper than blue, they go with everything black you already own, and with the right top they pass for trousers in a restaurant.

What makes a black jean look dressed up is a deep, even colour and a clean shape. I avoid heavy fading and rips, and I look for a leg that is either straight and long or softly flared, so it falls nicely over a heel.

Citizens of Humanity's Palma Long, at $250, is a long straight leg in a cotton and cashmere blend. FRAME's Palace flare is $300, and Khaite's Clara flare at $640 is the most polished of the lot. For a slimmer line, Toteme's Classic Cut is $430. If you want a bit more shape, AGOLDE's Spiral barrel leg is $290 and Studio Nicholson's Neive wide leg is $365.

Nili Lotan's Billie jean and Ossou's Flex Stretch are both $395, both straight and both simple. Wash them inside out in cold water, and not too often, and they will stay black for much longer. Length matters too: the hem should almost touch the floor in the shoes you plan to wear.

The top is what turns black jeans into an evening outfit. I think in three directions: silk, fine cashmere or a sharp blazer.

Silk is the easiest. Nili Lotan's Thelma shirt in ivory, at $590, looks lovely half tucked with the collar open. Khaite's Maeve T-shirt in cream silk cashmere jersey, at $1,080, is the more relaxed version.

Cashmere comes next. Khaite's Leni sweater in black at $1,180 has a polo collar, and a camel knit like Khaite's Lorelai at $990 softens all the black. Nili Lotan's Jori in ivory, at $1,390, is the chunky one for colder nights.

A black blazer over black jeans is the outfit I trust the most. St. Agni's 90s Wool Blazer is $619 and Nili Lotan's Diane is $890. For a grey alternative, St. Agni's Cocoon Blazer in concrete is $629.

Whatever the top, tuck it in or at least half tuck it. It shows the waist of the jean and makes the whole outfit look more intentional than a loose, untucked layer.

Shoes do most of the dressing up. A pointed pump with black jeans is a classic for a reason, because the toe peeks out from under the hem and makes your legs look longer. Khaite's Jett d'Orsay pump in black patent and Cecilia pump in black leather are both $980. By Far's Prudence 45, at $360, has a lower block heel that is easier to walk in.

For something more relaxed, By Far's Dasha thong heel and St. Agni's pointed mule in coffee, at $359, look good with a cropped flare.

The bag should be small and a little special. Mansur Gavriel's Moon Sling in black is $595, By Far's Kimberly bowler is $312, and Khaite's Mini Olivia hobo in black suede, at $1,580, is the one I would carry to dinner.

Jewellery is the final touch. Gold hoops or one chunky bracelet go a long way against all that black, and they are the easiest thing to change from one night to the next. Khaite's Cecilia has a slightly lower, curved heel that is kinder over a long night.