In a saucepan over medium heat, place the beaten eggs and egg yolks, passionfruit pulp and lemon juice. Using a whisk, stir constantly so the egg doesn't cook. After sugar has dissolved, slowly add bits of butter until it melts. Reduce heat to low, keep constantly cooking and stirring until the passionfruit curd thickens.
Stir or whisk frequently until the passion fruit curd thickens. This can take up to 10 - 20 minutes (the time depends on the bowl and the heat). The most accurate way to ensure that the passion fruit curd is cooked well is to use a temperature probe and check the temperature of the curd often, in between whisking.
Conversely, if you want the passion fruit curd to be very thick and spoonable (like Greek yogurt or pastry cream), then you will need to add more egg yolks (about 2 more than directed in the recipe here). I like to be able to make this passion fruit curd and then store it in the freeze for up to 3 months.
I prefer to add egg yolks because it yields a richer and thicker passion fruit curd. But if you prefer it runny, then you can reduce the amount of egg yolks, OR replace 2 of the egg yolks with 2 whole eggs.