In a heatproof bowl, whisk the water for blooming, vanilla bean paste and gelatin until no lumps remain. Set aside.
In a deep pot, combine remaining water, the honey, brown sugar and sea salt. Cook, on medium and stir until the sugar just melts. Turn heat to medium high and cook, without stirring, clipping a candy thermometer to the pot.
Once the sugar mix reaches 245-250 F, pour into the bowl of your stand mixer fitted with a whisk attachment and let cool for a few minutes.
Begin whisking the mix on low, and add in the gelatin. Turn the mixer to high and continue whisking for about 10 minutes, until the marshmallow fluff is thick and very light in color. You’ll know it’s done when it begins to pull away from the sides of the bowl. Add the butter to the marshmallow fluff when it’s done, and whisk to just to incorporate.
While it whisks, melt the chocolate in either a double boiler or in the microwave, stirring every 15 seconds (once it is mostly melted, take off heat and stir until smooth).
Spray or rub a 13x9 inch cake pan with a flavorless oil.
Once marshmallow fluff is ready, pour melted chocolate in and stir 2-3 times, leaving big streaks of chocolate. You could also do this by layering in thirds: adding marshmallow to the pan, some chocolate, swirling, and then mallow, then chocolate etc.
Pour fluff into pan and use spatula to get as much as you can from the bowl. Cover with foil and leave to set at room temperature for 6 hours or in the fridge for 3 hours until marshmallow is completely set.
To slice: remove the marshmallow from the pan and set it on a counter dusted with powdered sugar. Oil a chef's knife and slice the marshmallow into one inch squares (or any size you like). Set the powdered sugar in a bowl and dip each marshmallow in the sugar to coat, rubbing the marshmallows together so the mallow is well coated. Store in an airtight container, they'll last about 3 weeks.