Begin by brewing your strong chai tea. Place two tea bags in a large heatproof jug and pour boiled water over these. Leave to sit for about 10 minutes and then remove the tea bags. Place in the refrigerator to cool for about 30 minutes (this is factored in to the prep time).
Place your gelatine sheets in a bowl and cover with ½ cup of your brewed tea. Leave to soak and soften for at least 10 minutes.
Meanwhile, place the egg whites in the bowl of an standing mixer fitted with a whisk. Beat these to soft peaks form and set aside.
In a deep sided saucepan, add the sugar, liquid glucose and remaining ¾ cup of strong tea. Bring this to a boil over a medium high heat, stirring occasionally until the sugar dissolves. Continue cooking over the medium high heat until this syrup reaches 265°F (130C).
Once the syrup reaches the required temperature, remove from the heat and carefully add the soaked gelatine. Take care as the mixture will bubble up and is very hot! Stir until the gelatine has dissolved.
Return the electric whisk to the egg white and beat on high until stiff peaks form. Then, slowly begin pouring the hot sugar syrup into the egg whites, while continuing to whisk.
Allow the mixture to continue beating on high for about 10 minutes, until it has begun to thicken and cool.
While the marshmallow beats, line an 8" square deep sided baking tray with plastic wrap and grease this with flavorless oil.
Stir together the cornstarch and powdered sugar. Sift about ⅓ of this mixture into the prepared tray, covering the base and sides in a layer.
Once the marshmallows have been beating for about 10 minutes and are noticeably thickened, pour this into the prepared baking tray and smooth with a spatula. Leave to set for about two hours.
After two hours, sift another ⅓ of the cornstarch mixture over the top and tip out onto a piece of parchment paper. Remove the plastic wrap.
Oil the blade of a large, sharp knife and slice the marshmallows as desired. Re-oil between slices or whenever you feel the blade is becoming sticky. Dredge the pieces in the remaining ⅓ of the cornflour mixture.