Belgian Ale Moules with Cream and Triple-Cooked Tallow Frites

Method

1. Clean the mussels under cold water: tug the beards off towards the hinge and scrape off barnacles. Discard cracked ones and any open ones that don't close within a minute of tapping. Keep them in the fridge under a damp cloth.

2. Peel the potatoes, cut them into 1 cm sticks and rinse until the water runs clear. Bring the water and salt to a boil in a pot (20 cm) over high heat, add the potatoes, then lower to medium-low heat and simmer gently for 7 min, until a knife slides in easily and the edges look slightly fuzzy, but before they break up. Drain very carefully, spread on a rack and chill uncovered in the fridge for at least 30 minutes: that dry, roughened surface is what becomes a glassy crust.

   Add in this stepFloury potatoes 600 gWater (for blanching) 1½ LSalt (for the blanching water) 3 tsp

   high heat→medium-low heat

3. Melt the dripping in a deep, heavy pot (22 cm, 2×: pot size, number of batches), no more than half full, and heat over medium-high heat to 140 °C (use a thermometer). Fry the chilled potatoes for 5 min per batch, until a thin dry skin forms but they barely colour. Drain on a rack and cool for 15 minutes. Never leave the hot fat; smother any flames with a lid and never pour water on it.

   Add in this stepBeef dripping (or sunflower oil) for frying 1½ L

   medium-high heat

4. Finely chop the shallots, cut the celery into tiny 3 mm dice, strip the thyme leaves from the stems and chop the parsley.

5. Reheat the fat over high heat to 185 °C and fry the potatoes for 3 min per batch (×2) until deep golden and glassy-crisp. Drain, sprinkle with flaky salt and keep warm on a rack in a 100 °C oven. Turn off the fat.

   Add in this stepFlaky sea salt ½ tsp

   high heat

6. Melt the butter in a wide lidded pot (24 cm) over medium-low heat. Add the shallot, celery, thyme and bay leaves and cook gently for 5 min, until soft and sweet with no colour.

   Add in this stepButter 25 gShallots 2Celery stalk 1Fresh thyme sprigs 3Bay leaves 1

   medium-low heat

7. Raise the heat to high heat and pour in the ale (it will foam up). Boil for 1 minute to cook off its harsh edge, then add the mussels and pepper, cover tightly and cook for 5 min, shaking the pot once or twice, until they have all opened. Lift the mussels into warm bowls with a slotted spoon and cover with a plate; discard any that stayed closed.

   Add in this stepBelgian-style blonde or abbey ale 150 mlLive mussels in their shells 1,000 gBlack pepper to taste

   high heat

8. Pour the cooking liquid into a small pan, leaving the last spoonful behind in case it holds grit. Boil it over high heat for 3 min until reduced by about a third, then whisk in the cream and mustard and simmer until it lightly coats the back of a spoon. Remove the bay leaves, stir in the parsley and pour over the mussels. Serve with the frites and mayonnaise.

   Add in this stepHeavy cream 80 mlDijon mustard 1½ tspFlat-leaf parsley, chopped 2 tbspMayonnaise 4 tbsp

   high heat