I started making Vanilla Slice a few weeks ago. According to my family the Vanilla custard let me down - the pastry was yum, the custard needed work. The consistency wasn't right, there wasn't enough vanilla, I thought it was far too sweet etc. etc. So the family has been testing different custards; cream/milk, whole egg/egg yolks, amount of sugar, different flour/starch blah, blah, blah. Finally I'm happy & they are too with the custard in the Vanilla Slice.

This recipe was designed specifically to be made with Bakers' Magic gluten free flour. The finished baked product will not be the same if you use another gluten free flour and you will need to adjust the recipe, particularly if the flour you're using contains rice flour. 

Ingredients

1 quantity of Fabulous Flaky Pastry or other flaky pastry   

Custard

300 g Thickened cream (I used a 300 ml bottle)

600 g Milk (full fat)

60 g Maize starch 

120 g Sugar

6 Whole eggs (total weight 325 g)

2 Egg yolks (total weight 38 g)

20 g Vanilla essence

1 Vanilla bean

50 g Butter

extra icing sugar for dusting

A few tips:

Cream/milk: It is unlikely that you will get 300 g of cream out of the 300 ml bottle, make up the little bit that is missing with milk.  

Maize starch: Different flours/starches change the sweetness of the custard & the consistency. The custard is sweetest & sets better when maize starch is used. Maize starch can be substituted with potato starch however you will need to add more than 60 g & the sweetness may need to be adjusted.

Sugar: Initially the amount of sugar in the recipe was 200 g, I based this amount on a number of recipes found in cookbooks & on the web. I found the custard simply too sweet. I can't eat a whole piece of a bought Vanilla Slice whereas I can eat more than one piece (but shouldn't) of this Vanilla Slice. Will the custard be sufficiently sweet for you? Test a little of the custard near the end of the cooking period & adjust if necessary.

Eggs: Egg yolks make the custard beautifully rich. I started out making the custard with only egg yolks however when my stored egg whites reached 16 I decided the whites can go into the custard as well. I use 700 g/dozen sized eggs & the size of the eggs makes a huge difference to whether the custard will set or not. For those of you with your own fresh supply of eggs use the number of grams of eggs as your guide.  

Method

Make the flaky pastry according to the method described for Fabulous Flaky Pastry or Flaky Pastry until it is ready to be rolled out for use. I used Fabulous Flaky Pastry for the Vanilla Slice pictured above.  

Turn oven on to 210 - 220 C.

Line 2 baking trays with baking paper. Cut another 2 pieces of baking paper a little bigger than the size of your slice tin. I used a high sided slice tray (30 x 20.5 cm with a height of 5 cm) to put the Vanilla Slice in.

Roll out 1/2 the pastry to a thickness ~2 - 3 mm. Cut the pastry to be slightly bigger than the slice tray - the pastry will shrink a little when cooked. Transfer this pastry to one of the baking trays. Cover the pastry with another piece of baking paper & put another baking tray on top.

Repeat the step above with the remaining pastry.

Keep the pastry off cuts (if there are any).

Bake the pastry at ~210 - 220 C for 15 - 20 mins. The time & temperature will depend on your oven. If your oven struggles to get to temperature bake the pastry for slightly longer.

Take the top tray off each of the baked pastry & allow the pastry to cool.

Line the slice tray with non stick paper so that the paper overhangs the edges.

Transfer one of the pastry pieces to the slice tray. If it doesn't fit in gently cut bits off the pastry to make it fit. The pastry is easier to cut when it is cooler. If the pastry isn't quite the shape you wanted it don't despair. Grab a clean tea towel or something similar & wedge it between the side of the tray & the non stick paper. This will "stop" the custard from expanding too far off the pastry.  

Making the custard

Put the cream & milk together in a container.

Split the vanilla bean with a sharp knife along its length.

Gently scrape out the seeds & put them into the milk. I put the pod into the milk/cream & get my daughter to get the seeds out.

Thermomix

Put ingredients into the TM bowl apart from the butter.

Cook at 90 C for 12 mins at speed 4. (If halving the mixture cook at 90 C for 10 mins). 

Add butter & mix for 15 sec at speed 4.

While the custard is still hot, pour it onto the pastry base in the slice tray. 

Immediately transfer the other pastry piece to the top of the custard.

Set aside to cool.

Stove Top

On the stove top the custard can be made in a saucepan or in a double boiler. There is more control of the temperature in a double boiler & the custard is usually very smooth. If making the custard in a saucepan have on hand a stab blender. If the custard is lumpy blitz it with the stab blender.  

Set aside the butter.

Mix a little of the cream/milk with the maize starch to make a paste in the saucepan or top of a double boiler.

Add the remaining cream/milk, sugar, vanilla essence, eggs (whole & yolks). 

Stir over low/medium heat until it starts to thicken. Turn off the heat or lower the heat & stir the custard at this temperature for ~4 mins. 

Add the butter & stir it in.

While the custard is still hot, pour it onto the pastry base in the slice tray. 

Immediately transfer the other pastry piece to the top of the custard.

Set aside to cool. When it has cooled sufficiently transfer the tray to a fridge. 

Prior to serving dust the top of the slice with icing sugar. Alternatively use vanilla icing, passionfruit icing etc. 

To cut it lift the slice out of the tray by holding on to the non stick paper on either side. It is easier to cut when cold (I love Vanilla slice when the custard is cool but not cold - I tend to tidy up the slice along the edges before I put it into the fridge).  

The number of serves will depend on how big you make the pieces. If you cut the slice into ~5 x 5 cm pieces there will be at most 24. A piece this size will contain ~5 g or ~ 1 tsp of sugar excluding the topping.