Preheat oven to 375°F (190°C).
Line two baking sheets with parchment paper or silicone mats.

Melt butter in a medium saucepan, then remove from heat.

Add oats, sugar, flour, corn syrup, milk, vanilla extract, and salt to the melted butter.
Mix well.
Drop by spoonfuls onto the prepared baking sheets, spacing about 3 inches (7.5 cm) apart.
Flatten slightly with the back of a spoon or use a spatula.
Bake for 6-8 minutes, or until the biscuits are golden brown.
Let cool completely on the baking sheets.
Once the biscuits are cool, sandwich them with passion fruit curd to make biscuit sandwiches.
Passion Fruit Curd:
Cut the passion fruits in half and scoop out the pulp and seeds.
Place the pulp and seeds in a saucepan with the lemon juice and bring to a boil.
In a bowl, whisk together the eggs and sugar, then add the passion fruit and lemon juice mixture, whisking constantly.
Return the mixture to the saucepan, add the agar-agar, and bring to a boil, whisking constantly for 1 minute.
Remove from heat, then add the butter. Mix until the butter is fully incorporated.