For such a relatively young dish, the humble crumble has rapidly evolved to become a national institution. It started life as a sad apology of a dessert, born from rationing during the Second World War, when not even the most frugal housewife could guarantee she had enough flour, margarine or sugar for the luxury of a pie case. Instead, she worked the ingredients she had and scattered them sparsely over a medley of fruit to create the early prototype of a fruit crumble.
The wartime pudding endured, its frugality cherished by allotment holders, who recognised the topping as a crafty way to conceal overripe plums or the spongy pap of a windfall apple. Over the years, it has remained a firm favourite — the soft, sweet underside of a crumble topping, sodden with nostalgia, and the warm, biscuit aromas evoking memories of childhood teas and roast lunches.
It has continued to evolve, moving with generational trends. While the home economists of the 1990s pared back the butter and sugar in the topping, the current enthusiasm for “twists on a classic” has seen oats and nuts make their way into the mix. No longer is the crumble topping used to conceal the worst fruit; now it’s used to celebrate the best, and is a regular on the menus of gastropubs and fine-dining restaurants. For many, though, it’s still a pudding where home-made versions are best.
The classic recipe
Serves 4-6
INGREDIENTS
FOR THE TOPPING
Heat the oven to 180C (non-fan 200C). Tip the rhubarb, sugar and orange zest into a baking dish (5cm deep, 28cm long and 20cm wide), then toss together.
Rub all the topping ingredients together, spoon over the fruit, then bake for 30-35 minutes.
The rhubarb
At this time of year, forced rhubarb brings a splash of colour to the table. The plants are grown in dark sheds and produce stalks that are sweeter, more refined and less fibrous than the thicker, greener garden varieties. Look for blush-pink stems that are firm, rather than bendy, and shop for British-grown varieties.
The filling
Rhubarb can handle bold flavours, but often less is more. So, when experimenting, start by introducing a single ingredient, rather than going with too much at once.
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Orange zest is a classic pairing, but lemon, lime or grapefruit zest will also give a lift. Ground cinnamon, cardamom or nutmeg are all warm spices — try mixing 1 tsp of your choice into the crumble topping, or toss with the filling.
Crystallised or stem ginger, finely diced, will add texture as well as flavour, as will plump sultanas that have been soaked in warm water or orange juice. Substitute some of the rhubarb with a handful of fresh (or, at this time of year, frozen) strawberries or cranberries. You could even add chunks of bramley apple, but consider adding another tbsp of sugar, as this is a notoriously sharp-tasting variety.
The sweetener
Rhubarb is known for its tartness, which is something that should be embraced. Don’t be tempted to go overboard heaping sugar into the filling. Remember that the topping also contains sugar, and the pudding is often served with custard or ice cream anyway, so 2 tbsp caster sugar is plenty for 500g rhubarb. This can also be replaced with 2 tbsp honey.
When it comes to the topping, caster sugar is the traditional ingredient, but it’s a common trick to substitute half of it for demerara or muscovado sugar, to introduce a dark, molasses flavour.
The thickener
Rhubarb has a high water content (94%), so when it cooks, it gives off a lot of liquid. Because it has been tossed in sugar, the liquid will thicken slightly into a syrup. Whether or not it should be thickened any further is something that divides opinion.
Lots of chefs would be horrified at the thought of doing anything to alter the sweet poaching syrup, but those who don’t like such a juicy crumble might turn to a traditional thickener, such as cornflour or tapioca flour, and mix 1 tbsp with the raw rhubarb before putting on the crumble lid and cooking the pudding.
The crumble topping
The more butter and sugar, the “shorter” the crumble topping. Older recipes often contain the highest ratio — Larousse Gastronomiqe has a recipe with 1:1:1 of flour, butter and sugar — which is harder to “rub in” than the amounts suggested by modern recipes, and the result behaves more like a shortbread dough. Aim for a texture more like little pebbles than granules; using slightly chilled butter will help with this. When it cooks, a topping loaded with butter and sugar quickly bubbles into a golden crust with caramelised edges. And what it lacks in nutritional value, it more than makes up for in taste and nostalgia.
The modern-day crumble often works along the ratio of half the amount of fat to flour, with a little less sugar (such as 200g flour, 100g butter, 75g sugar). It’s less indulgent, but more textured, arguably healthier, and it doesn’t catch as quickly during cooking.
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A crumble topping doesn’t wholly rely on the flour to rise or bind, as with bread or pastry. This means there’s more room for experimentation. Lots of recipes substitute up to half the plain flour with porridge oats, or a quarter of it with ground almonds, while other ingredients make a simple addition, such as chopped nuts, granola or polenta.
For a gluten-free alternative, pair quinoa flour with ground pistachios, or rice flour with ground almonds, then add butter and sugar and rub together.
The pie dish
Bear in mind that the dish you use will affect your crumble-to-fruit ratio. A shallow baking dish might result in a near 50:50 ratio of rhubarb to topping, while a deeper soufflé dish generally holds more fruit, with a thinner crumble lid.
The cooking
Some recipes suggest precooking the filling; others suggest precooking the crumble topping so it remains crunchy. I find that the former stews the rhubarb to a pulp, and the latter is an unnecessary extra step. It certainly creates a crunchier topping, but robs the diner of that delicious, soggy layer where the streusel-type topping meets the sweet filling.
The twists
Rhubarb crumble has become embedded in Britain’s gastronomic heritage, but the plant originally came from China and stands up to exotic additions: plump goji berries and a pinch of ground star anise nod to rhubarb’s heritage. For a Middle Eastern twist, toss the rhubarb in a dash of rosewater, use ground pistachios in the topping and serve it with Greek yoghurt. Fresh green herbs also stand up well to rhubarb — chopped lemon thyme with some blueberries and a granola topping is a great combination. Bring some European decadence to mini crumbles by adding a dash of Grand Marnier to the filling and crushed amaretti biscuits to the topping.