Preserving sweetness during baking without sugar noob here (both to this site and to cooking in general!).  For health reasons I can't really do sugar, and the low-carb thing has saved my life (literally).  I am trying to do more low-carb baking at home.  The topic of non-sugar sweeteners have been discussed at length (pros/cons, how to substitute, etc).  I have used stevia at low temperatures to great success (making home-made drinks, chocolates, gummies, etc).

However, when I try baking with stevia, monk fruit, and/or erithyrol, the batter/dough tastes very sweet, but after baking I cannot taste the sweetness at all.

It's important to note that, unlike other questions, I already (a) can taste the sweetness in these alternative sweeteners (no genetic issue, and I'm okay with aftertastes), (b) have used and enjoyed these sweeteners at low-temperatures, and (c) the sweetness seems to disappear during baking regardless of the sweetener used.

I have already tried:


changing the sweetener and mixed sweeteners together (swapping stevia for monk-fruit, mixing them together, etc).  Stevia, for example, claims to be heat-stable, and others have claimed success when baking with stevia.
changed recipies (cookies, cakes, breads, brownies, etc) and quantities (more sweetener, less; more baking soda/powder, less, etc)
changing temperature and cook time


Given (a) that sweeteners like stevia claim to be heat-stable, (b)others seem to have success when baking with them, and (c) I've used these sweeteners with success at low-temps, what could be causing the loss of sweetness during the baking process?  Are there any known interactions with, say, vinegar or baking powder that would change the sweeteners during cook-time?
I hate answering my own question, but after a month I did (finally) find a pseudo-answer      that works for Stevia.  I've not yet tried it for any other sweeteners.

Melt into fat and freeze it

For example, the recipe I use for cookies needs four (4) tablespoons of melted butter.  I started by melting two tablespoons in butter (well, 1TB butter and 1TB cocoa butter but semantics aside...), and mixed half a tablespoon of stevia into the melted butter.

Then I poured the Stevia-butter mix into molds and froze until it was solid.

I proceeded with the rest of the recipe as normal, but after everything was mixed, I took the frozen Stevia-butter, chopped it into very tiny shavings/pieces, and mixed it into the batter.

Poured the cookies on the tray, and baked in the oven.  Result: nice, sweet, almost zero carb (~0.05g) cookies!!!

My working theory

I'm not confident in my theory, but I think the fats - especially saturated fats - will protect the Stevia early during the baking process. Couple that with Newton's law of cooling (ie, although the batter is at room temperature the sweetener is at sub-freezing temps, and will therefore take longer to heat up than the rest of the batter).  While the batter cooks as normal, the fats will melt into the batter, revealing and mixing the sweetener with it.  This minimizes the time the sweetener is exposed to the full-force heat of the oven, which prevents it from degrading under heat.

This may not be the best process for fluffy or flaky goods like breads, but for dense, sweet goods like cookies, muffins, brownies, etc, it works well. 

Yet again, that's just a working theory....