Because of the relatively large proportion of spelt in this recipe, I typically do a cereal mash. The process is quite straight-forward for Brew in a Bag, but may require some modification for other mashing regimes. I'm still a little ambivalent about the best time to add the spelt porridge to the main mash. Some of my recent beers made with the process below have had lower head-retention than I'm used to, and I'm still trying to work out if that is from using a more modified pilsner malt, or from including the spelt porridge in the first protein rest.
Crush spelt separately to consistency of grits. For me, that means running it through my Corona mill twice on a fairly tight setting (too tight and the mill sticks).
Bring the spelt grits to a boil in a large saucepan with a few litres of water (subtract this from the volume of your main batch, or take it directly from the liquor in the main kettle). Keep at a boil, stirring to prevent scorching, until it forms a thick porridge: usually 15-20 minutes. This stage can be done prior to brew day, with the cooled spelt porridge stored in the fridge till required. [NB: I often throw in a handful of crushed pilsner malt as well (yes, a handful, I don't measure it). I think the enzymes convert some of the sugars as mix passes through the conversion temperatures on its way to a boil. Sometimes I'll let it rest for ten minutes at around 150°F first.]
Heat main mash liquor and dough in with grist and spelt porridge, aiming for an initial temperature of 131F. You may need to break up the spelt porridge with your hands if you stored it before use. Keep at this temperature for around 15-20 minutes. [Optional step: you can also include an earlier rest at around 113F. This may aid with lautering and possibly increase phenolics from any brettanomyces strains.]
Raise mash to around 145F. Keep at this temperature for 40-50 minutes.
Raise mash to around 154F. Keep at this temperature for 20 minutes.
Raise to 168F. Mash out and lauter. Top-up with water to reach your desired pre-boil volume. Proceed with boil.
