Grease microwave safe bowl and electric stand mixing bowl with vegetable shortening. Set aside.

In greased microwave safe bowl, microwave mini marshmallows and water for 90 seconds and then stir. Microwave for another 30 seconds until marshmallows are a soupy consistency. Be careful not to burn marshmallows.

Using an electric stand mixer, pour melted marshmallows into greased mixing bowl. Add salt, lemon juice, corn syrup, and vanilla extract. Using dough hook, mix until incorporated.

Slowly add powdered sugar a cup at a time until all powdered sugar is added. Mix just until it is thick enough to hold its shape. It should be similar consistency to soft-serve ice cream.

Pour marshmallow fondant onto a vegetable shortening greased counter-top. Grease hands and knead marshmallow fondant for a minute.

Place marshmallow fondant in a greased, airtight container and allow to sit for a couple hours, or overnight before using.