Heat the oven to 110°C/225°F/Gas 1/4.

Carefully remove the mushroom stalks and chop the stalks finely.

Beat the butter with the mushroom stalks, garlic, tarragon, lemon zest and pepper to taste, then spoon into the cavities of the mushroom caps. Sandwich the mushrooms together in pairs and secure with cocktail sticks.

Lightly beat the eggs in a bowl and spread the breadcrumbs out on a plate. Dip each mushroom pair, first in the egg, then roll in the breadcrumbs. Repeat once more, then refrigerate for at least 1 hour.

Heat the oil in a deep-fat frier to 190°C/375°F or until a stale bread cube browns in 50 seconds. Fry a few of the mushrooms for about 5 minutes until golden brown. Drain on absorbent paper and keep hot in the oven while frying the rest.

To serve: remove the cocktail sticks and serve at once.