I found a recipe for a porter that has the following mash schedule.
4 lb (1.8 kg) Munich malt
3 lb (1.4 kg) Lager malt (US 6-row if possible)
2 lb (.9 kg) Flaked wheat (unmalted soft red wheat flakes if possible)
1 lb (.45 kg) Flaked oats
.75 lb (340 g) Cara Munich malt
.5 lb (227 g) Black Patent malt
.25 lb (113 g) Special B malt
.25 lb (113 g) Rice hulls (added to the mash)
Mix the flaked oats and flaked wheat with 1 lb of lager malt and mash in for 15 minutes at 150° F (65.5° C), then raise to a boil and maintain for 10 minutes. Have the other grains at protein rest, and raise to mash at 154° F (68° C) when you add the boiling unmalted grain to the main mash. Continue for 30-40 minutes, then mash out at 170° F (77° F), and maintain at least 165° F (74° C) during spargeing to keep the starch liquefied.
The directions seem clear, but I don't understand the purpose. What is going on here?