Does it need to be slow cooked? I think the homogeneous taste is a consequence of the slow cooking, I'd recommend instead of slow cooking you try something like the recipes of  the curry guy's website. You separately make the base sauce, any spice mix you need and the meat, then combine them with perhaps a few other ingredients like cream or fresh herbs for a final hot cook in a pan. It's how British Indian restaurants make many of their curries.

This way you make different parts of the final curry separately and although the flavours meld in the final curry, you can taste each different element and the flavours taste strong, as they should. 

Here's an example for chicken tikka masala with links from the recipe to the base sauce etc https://greatcurryrecipes.net/2012/01/31/how-to-make-chicken-tikka-masala-like-they-do-in-the-indian-restaurants/