Make a Soft Dough - In a large mixing bowl, add the dry ingredients: plain flour, sugar & salt. Stir to combine then add the yeast and mix.
In a separate jug, combine all the wet ingredients - egg, milk, melted butter and vanilla extract.
Slowly add the wet ingredients into the dry ingredients, mixing them gently with a spatula until just combined.
Transfer the dough to a floured surface and knead for 5-6 minutes to make soft dough. Add a little more flour at a time if needed while kneading until you achieve a soft dough.
Oil the inner pot of the Instant Pot and transfer the prepared dough. Secure the lid. Select the Sous Vide Button and adjust the temperature and time by pressing +/- to 33C & 30 minutes. Press start. After 30 minutes, the dough will have doubled in size.
Deflate the dough by punching down lightly then transfer the dough to making paper dusted with flour.
Roll it to a thickness of 1/4 inch, then cut rounds using a 3 1/2 inch cutter and a smaller cutter to make a hole. Gather the scraps and re roll them to cut more doughnuts.
Cover the cut doughnuts with kitchen towel and allow them to rise for at least 30 minutes or until doubled in size.
Place the inner stainless steel pot into the Instant Pot cooker base, and Insert the air fryer basket gently brushed with oil.
Place the Air fryer Lid on the cooker base. Select the AIRFRY programme and set the time to 3 minutes and the temperature to 180 C so the fryer can warm up.
After 3 minutes, Gently brush the doughnuts with melted butter (optional) and place 4 Doughnuts into the air fryer basket. Set the Temperature and Time to 180 C & 8 minutes and press Start. At 4 minutes, flip the doughnuts around. Repeat the process with remaining doughnuts.
To make the chocolate glaze, sift the Icing Sugar & Cocoa Powder in a medium bowl.
Add vanilla extract and 2 Tbsp Milk. Mix well until well combined. If you find the glaze too thick, add a little more milk and mix again.
When glazing the doughnuts, arrange the wire rack on a baking tin lined with parchment paper. Dip the doughnut into a glaze and transfer to wire rack. Repeat the process for the remaining doughnuts. Allow the chocolate to set before serving.