Metrowiec Cake Recipe: Polish Custard Layer Loaf

Metrowiec is a classic Polish dessert consisting of alternating vanilla and cocoa cake slices held together with smooth pudding cream. When sliced at a sharp diagonal, every portion displays distinctive diagonal stripes. Preparing it requires two identical loaf pans, and an elongated serving board or platter makes assembly comfortable. Chilling the assembled loaf thoroughly before slicing is essential so the cream sets firmly.

Ingredients

Sponge Dough

4 large eggs
180 g sugar
200 ml neutral vegetable oil
200 ml water
300 g all-purpose wheat flour
2 teaspoons baking powder
2 tablespoons unsweetened cocoa powder
2 tablespoons milk
a pinch of salt

Custard Cream and Chocolate Glaze

500 ml milk
2 egg yolks
70 g sugar
40 g potato starch
20 g all-purpose wheat flour
200 g unsalted butter, softened to room temperature
1 teaspoon vanilla extract
100 g dark chocolate
60 ml heavy cream (30% fat)

Step-by-Step Instructions

Line two rectangular loaf pans (about 25 cm long) with baking parchment. Preheat the oven to 170°C using top-and-bottom heat. Whisk the flour with baking powder and salt in a bowl.
Beat the eggs and sugar together until light, pale, and fluffy. With the mixer running on low speed, slowly stream in the oil, followed by the water. Fold in the dry ingredient mixture in batches, stirring only until no dry flour pockets remain.
Divide the batter into two equal portions. Sift the cocoa powder into one portion and add two tablespoons of milk, mixing gently until smooth. Pour the light and dark batters into their prepared pans. Bake for 35 to 45 minutes, until a wooden skewer inserted into the center comes out clean. If both pans cannot fit side by side on one oven rack, bake them consecutively. Cool both loaves on a wire rack.
For the custard cream, bring 350 ml of milk to a boil with sugar and vanilla extract. In a separate bowl, whisk the remaining 150 ml of milk with the egg yolks, potato starch, and flour until smooth. Pour this mixture into the hot milk, whisking constantly. Cook over low heat for about 1 minute after it thickens, stirring continuously to prevent scorching.
Cover the surface of the hot pudding directly with plastic wrap to prevent a skin from forming. Let it cool completely to room temperature. Beat the softened butter until pale and creamy, then add the cooled pudding one tablespoon at a time, whipping well after each addition. The butter and pudding must both be at room temperature to avoid curdling.
Trim both cooled loaves into slices about 1.5 cm thick. Spread a layer of cream onto one side of a vanilla slice, press a cocoa slice against it, and continue alternating colors horizontally down the length of your platter. Use the remaining cream to coat the top and sides in a thin, even layer. Chill for at least one hour.
Warm the heavy cream gently without boiling, remove from heat, and add the chopped dark chocolate. Let it sit for one minute, then stir until smooth and glossy. Pour the cooled glaze over the cake. Refrigerate for at least 2 more hours. Slicing at a distinct diagonal angle across the slice boundaries reveals the alternating stripes in every piece.

Timing and Yield

Preparation takes about 50 minutes, baking requires 35 to 45 minutes, and chilling takes at least 3 hours. Allow extra time for the cakes and cooked pudding to cool before assembling. This recipe produces roughly 14 generous slices, depending on cutting thickness.

Practical Tips and Variations

Even slicing: If the baked loaves formed rounded crowns, level them flat with a serrated knife before slicing. Uniform slice thickness makes stacking steady and creates a neat, clean cross-section.
Silky cream: If your cooked pudding has lumps, press it through a fine-mesh sieve before whipping it into the butter. Never mix warm pudding into softened butter, as melted fat will cause the filling to liquefy.
Assembly logistics: If your serving tray is not long enough to hold one continuous loaf, assemble two shorter logs side by side. Keep the alternating pattern consistent and slice both diagonally.
Clean cuts: Take the cake out of the refrigerator 15 minutes before serving. Use a sharp, long knife and wipe the blade clean between cuts to keep the stripes crisp and distinct.

FAQ

Why must metrowiec be sliced diagonally?

A diagonal cut passes through several vanilla and chocolate layers simultaneously, creating the signature striped presentation. Cutting parallel to the assembly seams would produce single-colored slices.

Can I prepare this cake in advance?

Yes. Once assembled, glazed, and chilled, store the cake covered in the refrigerator. Making metrowiec one day ahead allows the custard filling to soften the sponge slightly and lock the layers into place.

What should I do if the buttercream curdles?

Warm the bottom of your mixing bowl gently over a pan of warm water while beating on low speed, then whip briefly until smooth. Heat with care: melting the butter will turn the filling runny, requiring additional refrigeration to reset.