Now that the fog on the brain has cleared a little...
Your trying to make Croccante, Italy's spin on an almond-based brittle. Psiguyy, without a single bit of surprise on my part, has hit upon one potential woe in stirring. Another is potentially temperature control. Are you using a thermometer here?
I've seen brittles range in target temperatures from 238 (soft ball) to 300 (hard crack) and I personally prefer a cooler finish, so that I can pull a brittle slightly to thin it.
Okay. Here's what I would recommend....
One of things I always do when cooking syrups is to first rub a ring of butter inside the saucepan at a level where you expect the syrup to bubble up to when boiling. For me and my usual saucepan, that would be about 2 inches up from the bottom for this recipe. Having made this yourself, you'll have an idea of where the syrup reaches in a boil. Just take a stick of butter and run a light strip of coating, the width of the stick, around the inside perimeter. It doesn't take much butter at all for this and won't be enough to worry about in mixing into your syrup. When you do this, brushing down the sides with a damp pastry brush is practically unnecessary.
After the sugar is completely dissolved in the water and boiling, stop stirring and clip on a thermometer! I would also lower the cooking heat level to medium high, which will probably increase the cooking time to about 15-20 minutes, but add a little insurance to keep the sugar from burning. As you probably noticed, once the color of the syrup starts to darken and turn amber in color, it darkens quickly!
I would remove the syrup from the heat when the thermometer registers no higher than 240 degrees (F). Then add the sliced almonds and stir gently, but only enough to distribute the almonds somewhat. And the drier the day, the more quickly this is going to setup. And if your recipe tells you to "stir quickly", it means to work quickly...from the time you add the almonds and incorporate them to getting the stuff poured out.
Psiguyy's right about the alcohol in sprays, for sure! But unless you're spraying a layer so thick that it runs when you tip the pan, I wouldn't worry about using the stuff. But just a light coating on the sheet will do. (If you have some almond oil on hand, use that...!)
For this amount of syrup, I'm surprised that the almond amount isn't more like about 3-4 cups. The difference in using more almonds would make this recipe "crispier". And it would also change the behaviour of the syrup slightly in that more almond mass would cool the syrup more quickly.
So....
Don't stir during the boil;
Use a candy thermometer and stop cooking at 240 degrees;
And gently stir in the almonds, more or less folding them into the syrup, scraping from the bottom to cover the nuts.
Good going there, PA! I sure look forward to hearing how the next batch comes out!
And LOL about the menu! I wish I were just half as organized and efficient as you assume me to be!!!