Put around 500ml water in pot. Put potatoes in crisper basket or vegetable basked. Pressure cook on high for 6 minutes. Quick release the steam.

Transfer to a pan to actually mash as normal with some butter and seasoning and leave this on the side.
Empty the water out of the pot and give it a wipe.

Put some oil (just a bit) and the place the onions, carrots and minced beef/lamb in pot. Put on Sear/Saute on High - cook for about 8 mins stirring halfway, this will just soften the onions/carrots and brown the mince

Add in the garlic and mushrooms, stir through and cook for around 2 mins. Turn off the Sear/Saute

Add the flour, mixed herbs, brown sauce and tomato sauce. Add some salt and pepper to your taste. Stir through until you can no longer see the powder and pour the peas on top

Gently pour over the stock - DO NOT STIR

Pressure cook on high for 5 mins. Quick release the steam.
Now stir through and your base is ready

Spoon the mash that you made earlier over the meat base evenly but don't make it too smooth - leave it a bit rough

Grill on 190C for around 10 mins to crisp off the top, keep lifting the lid to check on it but it is personal choice how crispy you want the top