[Lazy Ant Brewing]

Can I partially mash a grain the evening before my brew day, cool it, and then reheat it separately the next day before adding to my strike water with the rest of my crushed grains? 

I need to partially mash Teff, an ancient grain, at 176 F then boil it for 20 minutes. Then cool it down to strike water temp of 152 F. 

My brew day is longer than I like so if it it won't mess up the brew, I would do the partial mash the evening before, cool the smaller amount in a cold water bath, refrigerate it overnight and then gently reheat it on my kitchen stove before adding it to the strike water with the rest of the crushed grains.

Is this feasible?

Thanks in advance for your advice,

[ynotbrusum]

You are describing an extended version of a cereal mash.  I have no experience with Teff, but the key will be whether the temperature changes you have planned (chilling it) will cause the substance to thicken excessively and then not loosen back up with the reheat. 

Most cereal mashes are used in a way that they are added from boiling to the main mash to raise the main mash somewhat to a desired temperature within a step mash schedule.  Once the cereal mash congeals, it may not work well as a step mash add without "sticking".  Even so, I would say, give it a try.  Found this for reference:

https://www.homebrewtalk.com/threads/teff-for-brewing.523052/

Cheers! 

[Lazy Ant Brewing]

Based on your reply, I'll do it the day of brewing and then add to my water for mashing as it nears the strike temperature.  It will be an adjunct since it's not available malted.  I do plan on toasting it prior to mashing.  Thanks again.

[EnkAMania]

I do overnight mashes with a sous vide and works well.  If you have a sous vide and a hop spider, something you might think about it.

[Lazy Ant Brewing]

I don't have a sous vide, but thanks for the suggestion.