Its almost sugar free - except for the dusting on top (which you can omit if you want) and the filling is light and airy, A perfect combo to the choux pastry sheets

I wanted to try something new, and I had the night free, so I decided to experiment. I'll try to simplify the recipe

Karpatka: Polish Vanilla Custard Slice 

Prep time:  20 mins | Cook time:  30 mins
(Printable Recipe) 

The Polish recipe calls for budyn, a powdered custard which might be tricky to find outside of Poland, so I used thick pouring custard instead. I used a 32 x 25 cm tray 

Ingredients 

For the choux pastry:  

 125g unsalted butter 

1 cup / 125g plain flour 

1 cup / 240ml milk 

5 eggs 

For the vanilla custard cream: 

750ml thick pouring vanilla custard (see alt in n.b)

2 eggs 

2 tbsp vanilla extract 

4 tbsp plain flour2 tbsp cornflour 

300ml thickened cream 

To serve: icing sugar 

Instructions 

Preheat oven to 220C (200C fan forced, 425F). 

To make the choux pastry:

1. In a medium pot bring milk and butter to a boil.
2. Add flour and mix vigorously with a spatula - eliminating the flour lumps, until the mixture comes away from the sides and forms a ball. This should only take a few seconds.
3. Transfer dough to a mixing bowl, add eggs one at a time and beat with an electric mixer until glossy and smooth.

To bake the choux pastry:

1. Line tray with non-stick baking sheet. (optional: grease with butter)
2. Spread pastry into a rough rectangle until the dough is only a couple of centimeters thick.
3. Place in the oven and bake for 25 minutes.
4. When ready, remove from the oven and allow to cool on the tray.

To make vanilla custard cream

1. While the choux pastry bakes, make the vanilla custard cream:
2. Place cream into a mixing bowl and whip with an electric mixer until it's fairly stiff - be careful not to over beat as it will turn into butter.
3. In a medium pot, combine custard, eggs, flours and vanilla extract. Whisk until smooth.
4. Place over low heat and cook, whisking, until the custard thickens.
5. move into a bowl and cover the bowl with clingwrap - to prevent skin to form. Cool to room temperature.
6. Add whipped cream to the mixture and whisk through. Refrigerate

To layer vanilla custard slice: Use a sharp knife (preferably bread knife), cut the pastry in half, the two sides will be yor top and bottom.  Spread custard cream over one layer, leaving a 2cm edge around and top with another pressing down gently. Trim edges if you want to get perfect squares. Otherwise skip this step if you prefer a more rustic look.

To serve: Use a sharp knife, cut the slice into 8 even squares. Dust with a little icing sugar and serve.

Nota Bene   

1. store the slice in the fridge and consume within 2 days. Bring to room temperature before serving. You may need to re-dust with some icing sugar.  
2. Alternative for thick custard cream:  

1. 1/4 cup custard powder
2. 2 1/2 cups (625ml) milk 
3. 2 tablespoons caster sugar (optional)

Recipe adapted from Wholesome-Cook