Strawberry Lemon Sheet Cake

Ingredients

1 stick plus 3 tbsp150 gunsalted butterSoftened. German butter is unsalted and has about 82 percent fat. In the US use unsalted butter; European-style unsalted butter is closest. In the UK use unsalted butter.
¾ cup150 ggranulated sugar
1 pinchsalt
2 tspvanilla sugar1 packet = 2 tsp (8 g). Sugar flavored with vanillin (artificial vanilla), sold in small packets of about 8 g. In the US use 1 tsp vanilla extract plus 2 tsp sugar for each 8 g packet; in the UK, vanilla sugar sachets, or 1 tsp vanilla extract plus 2 tsp sugar per sachet.
zest of one lemon
4large eggsGerman size M
2 ¼ cups270 gall-purpose flourIn German recipes plain flour means soft wheat flour Type 405 unless stated otherwise. In the US use all-purpose flour; in the UK, plain flour.
1 tspbaking powderGerman baking powder is sold in 15 g packets, each meant for about 500 g (4 cups) of flour. In the US and the UK use baking powder, 1 tbsp plus ¾ tsp per 15 g packet.

juice of one lemon
¼ cup50 ggranulated sugar
1 ½ tsp6 gagar-based gelling powderA plant-based gelling powder made with agar; it has to be boiled briefly to set. In the US and the UK use agar agar powder, using the amount on its package because strengths vary.
1 cup250 gquarkAny fat content. A fresh, mild and slightly tangy cheese with a spoonable texture, used in German cheesecakes, doughs and creams. In the US use full-fat Greek yogurt strained overnight, or farmer's cheese; in the UK, quark from the supermarket chiller (choose a full-fat one if you can find it).
1 ⅔ cups400 mlheavy creamIce cold. German cream for whipping has about 30 to 32 percent fat. In the US use heavy cream or heavy whipping cream; in the UK, whipping cream (double cream also works but whips faster, so watch it).

¾ cup plus 1 tbsp200 mlheavy cream
1 tbspgranulated sugar
1 tbspwhipped cream stabilizer1 packet = 1 tbsp (8 g). A packet of modified starch and sugar that keeps whipped cream firm; one packet is used for about 1 cup (250 ml) of cream. In the US use whipped cream stabilizer powder (sold online and in some baking aisles), or about 1 tbsp nonfat dry milk powder per cup of cream; in the UK, cream stabiliser powder (sold online), or a spoonful of mascarpone whipped in with the cream.
strawberriesTo taste
lemonTo taste
pistachiosChopped, to taste

Preheat the oven to 350°F (170°C) convection (fan). Line a baking sheet with parchment paper or set up an adjustable baking frame. (12 × 10 inches / 30 × 25 cm)
Beat the butter, sugar, vanilla sugar, salt and lemon zest vigorously for a few minutes. Beat in the eggs one at a time, mixing each one in thoroughly.
Mix the flour and baking powder and stir them into the batter.
Spread the batter in the pan and bake until golden. Then let it cool completely in the pan.

Put the juice of one lemon, the agar-based gelling powder and the sugar in a saucepan and bring to a rolling boil for 2 minutes, stirring all the time. (You should have about ¾ cup plus 1 tbsp (200 ml) of juice; if needed, simply top it up with water.)
Let the mixture cool for a few minutes, then stir in the quark and let it cool further until it is less than lukewarm.
Whip the cream until stiff and quickly fold it into the gelling mixture. Spread or pipe the cream over the cooled base and chill it thoroughly in the fridge.

Cook the strawberries in a saucepan with the remaining ingredients, except the agar-based gelling powder, for a few minutes until you have a chunky puree. Then stir in the gelling powder and let it boil for another 2 minutes.
Before you spread the strawberry mixture over the quark cream, let it cool until it is less than lukewarm.
Now chill the cake in the fridge again for about 2 hours.
For the decoration, whip some cream and pipe a dollop onto each piece with a piping bag. Decorate with strawberries, lemon and pistachios.

From German Pastry Chef. Full recipe with photos: germanpastrychef.com/recipes/strawberry-lemon-sheet-cake/