Dutch krokets (croquettes) are log-shaped nuggets of meat ragu, covered in breadcrumbs and deep-fried. The construction of the kroket sandwich basically involves stuffing one or two of these deep-fried snacks into a soft roll or slice of white bread and saucing with spicy mustard.

The inclusion of kecap manis (sweetened soy) may seem odd, but Dutch cuisine has a heavy Indonesian influence. The Netherlands was once a colonial power, and considered Indonesia the most prized colony of all.

(Makes 4)

For the bechamel sauce

2 tbsp (25g) butter

25g plain flour

Small grating of nutmeg

125ml hot milk

Sea salt and white pepper, to taste

For the filling

150g cold roast beef, chopped

½ small onion, very finely chopped

Small handful of button mushrooms, finely chopped

1 tsp kecap manis (sweetened soy sauce)

1 tbsp chopped fresh thyme leaves

For the coating

Plain flour

1 egg, beaten

Milk

Fresh breadcrumbs

Vegetable oil, for deep-frying

To serve

Soft white rolls, split open

Spicy mustard

To make the bechamel sauce:

Melt the butter in a small, heavy-based saucepan. Add the flour, stirring constantly, to make a smooth paste or roux. Keep stirring for several minutes. Grate the nutmeg into the milk, then gradually add it to the roux, stirring constantly. Bring this mixture gently to a boil, stirring, then simmer for about five minutes. Remove from the heat, season with salt and a little white pepper, and then let cool, covered with a piece of greaseproof paper to stop it forming a skin.

To make the filling:

Put all the ingredients into a food processor and blend until well combined. Mix with the cooled bechamel sauce and season with more salt and white pepper if necessary. Place the mixture in the refrigerator until it is well chilled (a couple of hours or so), then form into four log shapes (krokets), each about 7.5cm long.

For the coating:

Cover a plate with some flour. In a separate wide dish, mix the beaten egg with a splash of milk. Cover another plate with breadcrumbs. Dip each kroket first in the flour, then in the beaten egg mixture, and finally in the breadcrumbs to coat all over.

Meanwhile, pour some vegetable oil into a deep-frying pan or an electric deep-fat fryer and heat to 180C. Deep-fry the krokets in two batches for about five minutes or so, turning occasionally, until golden brown all over. Drain on paper towels. The cooked krokets can be kept warm in a low oven while you cook the second batch.

Serve the warm krokets in soft white rolls with plenty of spicy mustard on the side.

• 101 Sandwiches by Helen Graves is published by Dog'n'Bone at £12.99. Call 01256 302699, quoting GLR8UY, to buy a copy for £9.99, including free p&p.