@Pumpkinbumkin200 Yes, a great success! As with all my recipes, it is sort of an amalgamation of different recipes that I have found. I always start off by reducing the amount of sugar to at least half the suggested amount. This biscuit is only flapjack-like, in that it contains alot of porridge oats - but it also has some flour (which makes it more biscuit, or cake-like, depending how thin you make it). I am now intending to experiment with different flavours - by adding things like dried fruit, cacao and ginger - as I see this as a basic, bland starting point.
Anyway, here is the recipe exactly as I made it (you might want to increase the sugar, if you prefer standard levels of sweetness).
300g melted butter, 450g porridge, 150g caster sugar, 3 beaten eggs, 180g self raising flour.
Stir porridge oats in melted butter - then mix in the beaten eggs, followed by the flour. Press into greased baking tray (about 1cm thick - but I am going to try thinner as well, to see whether it will produce a crisper biscuit - variety is everything!). Bake at 180°C for about 20 minutes.
They started disappearing fast (we have a large, busy household and delicious food soon vanishes if not quickly hidden!) - so I froze some for packed lunches.