Many people might think this is too much fuss for a bowl of porridge as they would prefer to buy the sachet and get it done in the microwave in three minutes; what made me prepare this is the porridge I tasted in Belfast, Northern Ireland, done by an old lady in a manner which apparently is the original one, when the microwave didn't exist. During the last two years I managed to know the incredible qualities of the Oats to absorb huge quantity of milk and literally get filled of it, reaching a soft-granular consistency which is all what the porridge used to look like before the microwave era. The quantity of milk and porridge may vary according to the texture of your oat, I buy any random oat flakes from Asda or Tesco, not whole rolled oat yet not powder or too crushed. A whole rolled oat takes much longer than a broken oat flakes.
During the 15 to 20 minute wait, give it few additional stirs, this will prevent a film forming on top of the porridge.
The quantity ratio porridge: milk is roughly 1:5, maybe just slightly less. 50g of porridge with 250ml of milk. Adjust according to the type of oat flakes you use!