Line a 9x13 baking pan with parchment paper, leaving overhanging paper on the ends so you can easily lift out the marshmallows after they've firmed up. Brush the paper with oil so the marshmallows won't stick.

In the bowl of a stand mixer fitted with the whisk attachment, put 3/4 cup of water. Sprinkle the gelatin over it and let it sit. Add the vanilla bean seeds on top.

In a medium saucepan, put the sugar, corn syrup, and salt. Begin heating it, stirring to dissolve the sugar. Then stop stirring and let the sugar syrup come up to 238 degrees. It will boil for a while before it gets there.

Then, with the mixer on low, slowly pour the hot syrup into the gelatin. Gradually increase the speed until it is on high. Beat on high for about 12 minutes until the mixture is stiff. Beat in the vanilla.

Pour the mixture into the prepared dish, smoothing it out evenly.

Let sit, uncovered, for 3 hours (or overnight)

Turn out the marshmallow block onto a surface covered with confectioner's sugar. Peel off the paper and dust the whole top surface with more confectioner's sugar.

Spice the marshmallows into squares using a sharp, oiled knife or pizza cutter. They will resist a bit, but keep at it. As you cut each strip, turn it to coat the cut ends with sugar, and as you cut each individual marshmallow, do the same. All the sides should be well coated and not sticky. Lay the marshmallows out on a tray.

Store in an airtight container and eat within the week.