In a large bowl sieve in the plain flour and baking soda, add the brown flour, sugar, salt, oats and walnuts. Mix all of these ingredients well with a spoon before forming a well in the centre.
Now add the milk, golden syrup, black treacle melted butter and Guinness.
Mix all of these ingredients really well making sure you get all the flour from the bottom and there are no dry patches in your mix.
Your mix should look wet and porridge like in texture.
This mix should fill 2-3 average sized loaf tins. Ensure to grease your tins well and dust will flour before pouring the bread mix. You should fill the tins three quarters full. This should allow enough space for the bread to rise and come just over the top of the tin once cooked.
Pre heat the oven to 150°C and place the bread in the centre of the oven.
Cook at this temperature for 45 minutes, than, increase the temperature to 180°C and cook for a further 25 minutes.
The way to ensure the bread is cooked through is to remove it from the tin and holed the bread with a cloth close to your ear.
Now knock on the base of the loaf as if knocking on a door. You should get a good clear hollow sound.
A tip to keep you bread from drying too much while cooking is to place a shallow pan of water at the bottom of the oven while the bread is cooking, this will add a little steam to the oven helping the bread to stay moist.