Mustikkapiirakka

Ingredients

The base

• 150 gbutter, softened
• 100 gcaster sugar
• 1egg
• 250 gplain flour
• 1 teaspoonbaking powder
• a pinch of salt
• half a teaspoon vanilla
• or ground cardamom
• optional

The filling

• 500 gbilberries
• or blueberries
• fresh or frozen
• 60 gsugar
• or to taste
• 2 tablespoonspotato flour
• or cornflour
• see the note

The topping

• 200 gsoured cream
• or quark, or crème fraîche
• 1egg
• 50 gsugar
• 1 teaspoonvanilla
• optional

The tin

• a 24 cm springform tin
• or a shallow tart tin
• greased and lined

To serve

• cold milk
• or vanilla sauce
• or whipped cream
• coffee

Directions

1. Wash any foraged berries before use. Rinse them in a colander under cold water. Pick out leaves and stems. Do not soak them. Rinse briefly and drain them. Do not thaw them before baking. Add five minutes to the baking time. Toss the berries with potato flour or cornflour. It sets it into a soft gel rather than a liquid.
2. Beat the butter and sugar together. Beat until pale and creamy. Give it three minutes. Beat it in thoroughly. Add the vanilla or cardamom. Now add the dry ingredients. Add the flour, baking powder and salt. Fold them in until just combined. Do not overwork the dough. Mix only until the flour disappears. It should be a soft sticky dough.
3. Chill it for thirty minutes. Press about three quarters into the base. Press it up the sides by about three centimetres. Flour your fingers, or use damp ones. Aim for an even layer of about half a centimetre.
4. Toss the berries with the sugar and starch. Tip them into the base. Spread them level. Blueberries need less sugar. Taste a berry and judge.
5. Whisk the soured cream, egg, sugar and vanilla. Whisk until completely smooth. Pour it evenly over the berries. Any thick soured dairy serves. Bake at one hundred and eighty degrees. Give it about thirty-five minutes.
6. Add five if the berries were frozen. The topping should be set and lightly golden. Let it cool completely in the tin. Cut warm, it runs everywhere. Cut cold, it slices cleanly. Give it at least two hours.
7. Serve it at room temperature or cold. Cold milk is the classic Finnish accompaniment. Keep it covered. Wrap it well and thaw it at room temperature. Frozen bilberries keep a year.

Technique

• Toss the berries with potato flour or cornflour before they go in. The starch sets the juice into a soft gel as it heats rather than letting it run — two tablespoons for 500 g. Potato flour is the Nordic choice and thickens at a lower temperature, giving a clearer set.
• Do not thaw frozen berries. Thawed berries collapse and release all their juice at once, soaking the base; frozen ones release it slowly. Put them in frozen and add five minutes to the baking time.
• Cool it completely, at least two hours, before cutting. The filling sets only as it cools — cut warm it runs everywhere, cut cold it slices cleanly.
• Press the base evenly, about half a centimetre thick. Thick patches stay doughy and thin patches let juice through, and evenness matters more than neatness. Laying cling film over and pressing through it gives the most even result.
• Chill the dough thirty minutes before pressing. It is a soft sticky dough and very hard to spread evenly unfirmed.
• Do not overwork the dough. Mix only until the flour disappears — beyond that the gluten develops and the base goes tough.
• Blind-baking the base for ten minutes before the filling goes on gives a crisper result. It is optional and it helps.
• Bilberries are not blueberries. Bilberry is Vaccinium myrtillus, small, dark and wild; the cultivated blueberry is a different species, milder and sweeter. The easy test is the flesh — bilberry is deep purple-red throughout, blueberry pale green-white inside, which is also why bilberries stain hands, teeth and clothing.
• Taste a berry and judge the sugar. Bilberries are considerably more sour than blueberries.
• Rinse foraged berries briefly and drain them; do not soak them, since they are soft and absorb water.
• Cold milk is the classic Finnish accompaniment and surprises people who expect cream. Vanilla sauce, a thin pouring custard, is the other standard.
• Finland’s jokamiehenoikeus, everyman’s right, allows anyone to walk in forests and pick wild berries and mushrooms regardless of who owns the land, with responsibilities not to damage or disturb. It is genuine law and widely exercised. Much commercial picking is done by seasonal workers from abroad, whose conditions have been the subject of documented concern and legal cases.

Substitutions

• Blueberries replace bilberries, giving a milder and sweeter pie that needs less sugar.
• Frozen berries replace fresh and go in from frozen with five extra minutes.
• Quark or crème fraîche replaces soured cream in the topping.
• Cornflour replaces potato flour as the thickener.
• Cardamom replaces vanilla and is very Finnish.
• Crumbling the reserved dough over the top makes a crumble version instead of the cream topping.

Variations

• Mustikkakukko is the savoury-cased Karelian bilberry pie, quite different in construction.
• Karjalanpiirakka, the rye-crusted rice pastry, is Finland’s best-known piirakka and is savoury.
• Mustikkakeitto is a thin bilberry soup drunk hot or cold.
• Rahkapiirakka uses quark as the main filling rather than the topping.
• A lingonberry or crowberry version is made with the same base.
• Blåbärspaj in Sweden is the close neighbour version.

Frequently asked questions

What is Mustikkapiirakka?

Mustikkapiirakka is a dessert from Finland: bilberry pie eaten with cold milk or vanilla sauce.

How long does Mustikkapiirakka take to make?

Mustikkapiirakka takes 30 minutes plus chilling of preparation and 35 minutes of cooking. The recipe makes serves 8. It is rated medium to make.

What can I substitute in Mustikkapiirakka?

Yes, within limits. Blueberries replace bilberries, giving a milder and sweeter pie that needs less sugar. Frozen berries replace fresh and go in from frozen with five extra minutes. Quark or crème fraîche replaces soured cream in the topping. Cornflour replaces potato flour as the thickener. Cardamom replaces vanilla and is very Finnish. Crumbling the reserved dough over the top makes a crumble version instead of the cream topping.

What is the most important thing to get right in Mustikkapiirakka?

Wash any foraged berries before use. Rinse them in a colander under cold water. Pick out leaves and stems. Do not soak them. Rinse briefly and drain them. Do not thaw them before baking. Add five minutes to the baking time. Toss the berries with potato flour or cornflour. It sets it into a soft gel rather than a liquid.