Preheat the oven to 190 °C (fan oven).
Unroll the puff pastry sheet on a lightly floured surface and cut into 10 equal rectangular pieces (2 of the rectangular might be slightly larger).
Place them on a tray lined with parchment paper and cook for 15 minutes or until lightly golden brown.
Let the cooked puff pastries cool down and start making the creme diplomat.
Place the milk, butter, and vanilla paste in a saucepan and gently bring to simmer on low heat. Remove the saucepan from the heat.
In a bowl, whisk together the egg yolks and sugar until the mixture becomes pale and thick. Add the flour along with the cornflour and whisk to combine.
Add half of the hot milk into the flour-egg mixture, whisking well, and return the mixture into the saucepan with the rest of the milk.
Return the saucepan to heat and cook until it thickens, whisking continuously. Let it boil for a minute stirring continuously then remove from the heat. Let it cool down to room temperature.
When the pastry cream has reached room temperature, start whipping the double cream or whipping cream until you reach stiff peaks.
Whisk the pastry cream to loosen then fold in the whipped cream gently in 2 stages.
Split the puff pastries in half and put 1- 1 ½ tablespoon of diplomat cream on top of the half puff pastry sheet.
Place a couple of tablespoons of chopped strawberries on top of the diplomat cream and place the other puff pastry sheet on top. Repeat the same for all of the puff pastries.
Sprinkle on some icing sugar using a small sieve and place a piece of strawberry for garnish.