How to make lemon curd?

This was meant to be a "How to make lemon curd" post that left me with some egg whites that I didn't have the heart to throw away. I usually keep the leftovers in the fridge for later use (which never happens anyway). However this time, the egg whites came to good use. The lemon curd, the crushed meringue and some whipped cream made a simple yet satisfying dessert. It's relatively easy to make and I have tried to be as detailed as I can but if there is anything that is not clear, let me know.

For those of you who are not familiar with lemon curd, it is like custard but less sweet with an intense flavour from lemons. It's also sometimes described as lemon-flavoured butter. Whichever way you look at it - it is delicious! The only downside is that they can't be refrigerated for too long (generally upto one week). Feel free to taste and adjust the amount of sugar in the lemon curd. Since I had the lemon curd with meringue, which is very sweet, I made mine very tangy.

(About 6 servings)
Lemon Curd:
3 large egg yolks
50 g unsalted butter (at room temperature)
2 tbs caster sugar (for the lemon syrup)
1/3-2/3 cup caster sugar
3 tbs fresh lemon juice
1/2 tbs lemon zest

Meringue:
3 large egg whites
2/3 cup caster sugar
1/4 tsp salt or cream of tartar

To assemble:
2/3 cup whipping cream (I used 40 %)
4 tbs icing sugar/confectionar's sugar
1 tsp vanillin sugar/vanilla extract
Fresh fruits or berries (for garnish)

Method:
To cook the lemon curd you could use a double boiler or place a glass bowl with 1 inch of water on the stove. Make sure that the bowl on top does not touch the water underneath. I personally prefer not to cook the lemon curd in a double boiler or metal bowls because the lemon reacts with metals (resulting in a strange aftertaste). The best option is to use a heatproof glass bowl to cook the lemon curd in.

Separate the egg yolks from the egg whites and place the egg yolks in a heat-proof glass bowl or double boiler. When you separate the egg whites from the egg yolks, make sure that there is no trace of egg yolks in the egg whites (that you need to make the meringue). Place the egg whites in a clean and dry bowl, cover and refrigerate until needed. Cut the butter into small sticks and let it come to room temperature. Mix the lemon juice with the sugar (needed for the lemon syrup) and the lemon zest. Whisk the egg yolks until smooth. While whisking the egg yolks, gradually add the lemon syrup into the egg mixture. Place the glass bowl with the mixture on top of the cooking pot with the water (that should be on a simmer). Keep stirring the mixture until it thickens at very low temperature (on simmer). The lemon curd is not suppose to boil and get bubbly. If the water underneath is too hot, the lemon curd can start curdling and that's why it is cooked over simmering water that shouldn't touch the bowl on top.

Once the lemon curd has thickened (or reached the consistency of hollandaise), taste and add some more sugar as preferred and then add the butter sticks and stir until the butter has completely melted. Take the bowl away from the stove. Strain the lemon curd to get rid of the lemon zest and any lumps that may have formed. Allow the lemon curd to cool to room temperature first, stir and then transfer the lemon curd into a clean and dry jar. Cover and refrigerate for a couple of hours or overnight, until thoroughly chilled. Generally, you can keep the lemon curd refrigerated for upto one week.

To make the meringue, take the egg whites out of the fridge and let them come to room temperature. Preheat the oven to 150 C (about 300 F). Please don't use a bowl that is too wide to whisk the egg whites. Start whisking the egg whites with a handmixer at low to medium speed until foamy and bubbly. At this stage you can add the salt or cream of tartar. Continue to whisk and then add the sugar gradually when the meringue is at the pre-soft peak stage to make sure the sugar gets fully dissolved and now you can start whisking at medium speed. Soft peaks mean peaks that curl downwards when you remove the whisk from the mixture. The peaks that appear at the soft peak stage are still soft and not firm (unlike stiff peaks that remain stiff and straight when you remove the whisk).

Once you have added the sugar you will notice that the mixture gets really glossy, white and dense as you whisk. You have to stop whisking from time to time to check what stage you are at. It is only when you remove the whisk from the meringue mixture, you will be able to see what kind of peaks are formed. Once you have reached the stiff peak stage, you can stop whisking. At this stage the peaks should be stiff and somewhat, if not completely, straight when you remove the whisk. You will also notice that, the meringue mixture is so firm that even if you turn the bowl upside down, the mixture wont move. Take some of the mixture and rub between your fingers and check if the sugar has been completely dissolved.

Line an oven sheet with parchment paper. It's also a good idea to take some of the mixture that is left on the whisk and place them on the underside of each corner of the parchment paper to prevent the paper from sliding. Carefully spoon 12 cookies (or so) out of the meringue using two tablespoons onto the parchment paper. Don't try to flatten the meringue as you do this. Handle it gently. The meringue can sometimes deflate in the oven, if not handled gently. Once the oven is hot, lower the temperature to 90-100 C (about 200-210 F) and place the meringue in the center rack of the oven and allow it to bake for 1 hour and 10 minutes. Halfway through, open the oven and rotate the oven sheet so that all of them are evenly baked. Turn off the oven and let the meringue rest in the oven for some 4-5 hours or so, or overnight. Store them at room temperature in a clean and dry container.

The lemon curd and the meringue is best done a day ahead or at least 4-5 hours ahead of serving because the lemon curd has to be chilled and the meringue has to rest once it has been baked. To assemble the dessert, whip the cream with confectionar's sugar and vanilla extract/vanillin sugar until stiff peaks, ahead before serving and keep it covered and refrigerated until needed. Assemble the dessert in 6 wine glasses, by first placing whipped cream at the bottom of the serving glass. Even out the layer of whipping cream around the edges, so that the lemon curd doesn't sink through the holes to the bottom. Spoon in a small layer of lemon curd over it. Crush the meringue cookies and spread on top of the lemon curd (this will turn out a little messy). Repeat the process until you have lemon curd on the topmost layer (I noticed that it was difficult to make the lemon curd "stay" there. I would probably skip this step next time). Alternatively, you could also place the cream in a piping bag and pipe it out on top and keep it as the topmost layer. Garnish with fruits and/or berries, I served mine with physalis/ground cherries. For more variation, you could also layer with some crumbled pound cake and/or fruits, you could layer pound cake between the cream and the lemon curd. Serve immediately and cold!