Crispy Roast Potato Pan Gravy

Everyone deglazes the meat tin and nobody deglazes the potato one, which is a waste, because a tin of roast potatoes leaves behind fat, salt and a layer of caramelised starch that makes a surprisingly good gravy. This is the one to make when the meat is cooked on a rack or when there simply is not much in the joint's tin.

Ingredients

Makes about 550ml, enough for six plates

• 2 tbsp goose fat or dripping left in the potato tin
• 1 onion, sliced
• 2 cloves garlic, whole and lightly crushed
• 2 tbsp (30g) plain flour
• 650ml (23fl oz) hot chicken or beef stock
• 1 tsp Marmite or yeast extract
• 1 sprig rosemary
• salt and black pepper go easy, the tin is already salty

Kit

• Potato roasting tin
• Wooden spoon
• Whisk
• Sieve

Method

1. Tip the potatoes out of their tin into a warm serving dish and put them somewhere hot. Do not wash the tin. Those crusty pale gold patches welded to the base are toasted potato starch and they dissolve into gravy beautifully.

2. Pour off all but two tablespoons of the fat, keeping every bit of the stuck-on crust. If you roasted in goose fat, the excess is worth saving in a jar.

3. Put the tin over a medium heat on the hob and add the onion, garlic and rosemary. Fry for six or seven minutes, using the wooden spoon to work at the crust as the onions release moisture.

4. Stir in the flour and cook for two minutes. The mixture will look dry and lumpy because of the potato bits, which is fine, they break down once the liquid goes in.

5. Add a third of the hot stock and stir hard, scraping in long strokes across the base. You will see the pale crust lift and the liquid go cloudy, which is exactly what you want. Add the rest of the stock in two goes.

6. Bring to a simmer and cook for ten minutes. The potato starch gives this gravy a slightly softer, rounder texture than a flour-only one, and it will thicken more than you expect, so keep some hot stock at hand.

7. Whisk in the Marmite for depth and colour, since a potato tin gives you savour but not much darkness.

8. Strain through a sieve into a warm jug, pressing the onion through, and discard the garlic and rosemary. Season with pepper and taste before adding any salt at all.

Tips worth knowing

• Salt the potatoes before roasting, as usual, but remember that salt ends up in the tin and therefore in the gravy. Taste before seasoning.
• A tin that is black and burnt in patches will make bitter gravy. If the bottom looks like charcoal rather than caramel, use a saucepan instead.
• Parboiled and roughed up potatoes leave far more starch behind than smooth ones, which makes for better gravy as well as better spuds.
• This works with a tin of roast parsnips or carrots too, and those give a sweeter gravy that suits pork.

Keeping and reheating

Three days in the fridge, three months frozen. The potato starch means it thickens a lot on chilling, so reheat gently with an extra splash of stock and whisk it smooth.

Questions people ask