Marshmallow Slab:

Line an 8×8-inch square tin with parchment, and coat generously with oil. (See this recipe for the best lining technique!) Set aside until ready to use.

Fill a bowl with cold water. Add leaf gelatine, and set aside to soak.***

Meanwhile combine sugar, corn syrup or liquid glucose, remaining 120 milliliters water, and fine sea salt in a large saucepan. Bring mixture to a boil and boil, without stirring, until syrup reaches 240° F / 116° C on a candy thermometer.

When sugar mixture is near temperature, remove the soaked gelatine from the water and squeeze it to drain any excess water. Add gelatine mass to a large mixing bowl (if using a hand mixer), or the bowl of a stand mixer.

Carefully pour hot syrup into gelatine bowl. Mix on high speed for 2-3 minutes, until mixture begins to thicken. Add vanilla bean paste and continue to mix on high speed until very thick, about 8-9 minutes more.

Using an oiled spatula, scrape marshmallow mixture into prepared tin. Loosely cover with a well-oiled sheet of aluminum foil. Allow to set until firm, at least 4 hours or overnight.

Cutting and Coating:

In a small bowl, combine potato starch and icing sugar.

Cover a large chopping board with a sheet of parchment, and dust generously with starch-sugar mixture.

Turn marshmallow slab out onto dusted surface. Sift top of slab with more of the starch-sugar mixture.

Use a well-oiled knife to cut the slab into squares. I like to do six rows of six, which makes 36 generously-sized marshmallows.

Toss cut marshmallows in additional starch-sugar mixture, making sure all sides are coated.

Marshmallows will keep well for several weeks when stored in an airtight container at room temperature.