Do this step first to avoid running around to get it together when the time comes! Place a medium or large sieve over a mixing bowl. No butter! Ignore the butter in the background haha.
Add the soy milk, vanilla extract, agar agar powder, and pinch of salt to a small sauce pan. Mix to combine and leave on medium heat until it begins to simmer. It will simmer pretty quickly, in a few minutes.
In a small or medium-sized mixing bowl, combine the sugar, cornstarch, and Just Egg. Mix with a whisk until evenly combined.
Once the milk mixture has started to simmer, slowly whisk in half of it into the Just Egg mixture.
Next, slowly whisk in all of the mixture from the mixing bowl back into the pot with the remaining milk mixture. Whisk continuously on medium heat to cook and thicken the mixture. It should be thick enough to see the streaks of the whisk in it.
Turn off the heat. Scoop the mixture from the pot into the sieve you prepared earlier. Using a rubber spatula, press it through the sieve to get rid of any lumps in the mix. Don’t forget to scrape the outside bottom of the sieve to get any of the mix that collects there. Cover with plastic wrap and allow to cool in the fridge until it is not hot anymore, just barely warm.
Next, to make the whipped cream, pour 1 cup of Silk whipping cream into a mixing bowl.
Using an electric hand mixer with the whisk attachment, beat the cream for about 3 minutes, or until stiff peaks form.
Get your bowl of pastry cream from the fridge. It's easiest to mix with the whipped cream if it's still just slightly warm, before the agar agar sets. Add the whipped cream to the bowl with the pastry cream.
Whisk together until incorporated. If you still have lumps in the mix, you can pass it through a sieve again using a rubber spatula to get it through.
Place the mix into a piping bag and let it cool completely in the fridge.