Start with raw almonds, blanched and peeled, and food processes them to a very fine meal (I needed about 1.5 cups of nuts to make it work in my food-processor so the excess has been sealed and popped in the refrigerator). I never got it to turn to butter just sticky, fine meal.
Substitute the almond meal for flour at 4 to 1 (that is for recipe calling for 2 tbsp of flour use 8 tbsp of almond meal.
The result did not have the ugly color of the first experiment, though it was still a bit darker than the flour based curry. The texture was smooth on the tongue this time (you must get the meal very fine!) and nearly as think as the flour based recipe. The eye could still detect some grain structure, but it didn't detract from the experience of eating the dish.
The taste of toasted almond was detectable in the dish, but set off the usual flavors very nicely. However, the pure bulk of almond meal employed diluted the spiciness somewhat: you might wast to ramp up the hot a little.
I'm still considering trying hazelnuts, but I'm pretty happy with what I've got so far.
The substitution was fine meal made from raw almonds using about twice as much as the flour it was replacing (taking Michael's thoughts about starch levels into account). The results were mixed: grainy and a slightly unappetizing, nearly black color. The sauce gelled a bit at first, but lost the proper consistency sometime after I had half the usual amount of liquid added. Despite these short comings, the flavor was very nice.
I'll probably take another crack at it soon, and plan three adjustments from tonight's attempt:
- peel the almonds---I think the skins played a major part in the color situation
- grind the meal finer still, it may have to be butter
- increase the amount a bit more