So I decided to do a split brewday. Also I wanted to experiment with decoction. So the steps I did are below. I got this from
http://brewery.org/library/DecoctFAQ.html
* Strike temperature of 53C, stir well and rest for 20 mins
* Stir and take 1/3 of the mash. (If you use a large proportion of unmalted grains you can take less of the mash and add water and dry crushed grains to make up 1/3 of the total volume). Heat to 72C, rest for 20' (malt) to 40' (malt+grains).
* Bring to boil and boil for 15-30'
* Add back to reach a temperature of 65-67C, rest 15-35'
* Take 1/4 of the mash, boil for 15-30'
* Add back to reach a temperature of 70-73C, rest until saccharification is complete (30'-1h).
* No mash-out, start sparge immediately. (I do BIAB so not required.)

Grains
2kg Pilsner malt
2kg Flaked wheat
1kg Wheat malt
250g porridge oats.
Hops
Halletauer Mittelfruh 30g 60 mins
Halletauer Hersbrucker 30g 60 mins
Halletauer Mittelfruh 20g 15 mins
Halletauer Hersbrucker 20g 15 mins
Irish moss 15 mins
Yeast WLP300.
23l at 1050.
I mashed all the grain initially bar the porridge oats. I chucked them in with the decoction (is that the mash or the process???)
I've got to say it smelled lovely when it was boiling - sweet porridge.
Now my last Weiss I did the efficiency was pitiful. (Say it in a Roscoe P. Coltrane type way ) Pitteeeeefulll.
I took a reading after crash cooling some of the wort - 1055!!! Pre-boil!!!
Took it up to the boil and left for 15 mins with the lid on to sanitise.
I will finish the boil tonight.