Strawberry and mascarpone tart

Description

Digestives will work here, but something softer and with a more open texture will give the consistency I am hankering after. Posh biscuits, the sort that come in boxes rather than packets, are probably the best.

Ingredients

For the crumb base
250g/9oz almond, orange or sweet oat biscuits
75g/3oz butter, melted in a saucepan
For the filling
1 large egg
1 tbsp caster sugar
250g/9oz mascarpone cheese
2 drops vanilla extract
250g/9oz strawberries, hulled and thinly sliced

Method

You will need a rectangular tart tin with a removable bottom. I used a long, thin one, 34cm x 12cm/13in x 5in, but you can make it in something shorter and wider if that is what you have.
For the crumb base, melt the butter in a small saucepan. Crush the biscuits to a coarse powder. A food processor will do this in seconds or you can put the biscuits in a plastic bag and bash them with a rolling pin. Do it gently or the bag will split. Thoroughly mix the crumbs with the butter. Spoon the crumbs into the tart tin and smooth them into the corners and up the sides. Press firmly, but not so hard that they become compacted. The biscuit base is better when short and crumbly. Refrigerate until the base has set.
Make the filling. Separate the egg, put the yolk in a bowl with the sugar and beat for a few seconds until thoroughly mixed. Beat in the mascarpone until you have a custard-coloured cream. Stir in a little vanilla extract; a couple of drops should be enough. With a clean whisk, beat the egg white until it stands stiff, then fold it into the creamed mascarpone.
Spoon the mascarpone into the biscuit crust, spreading it smoothly right out to the edges. Hull the strawberries, slice them thinly, then arrange them on top of the mascarpone. Keep cool, removing the tart from the refrigerator a good twenty minutes before serving.