Hi RP- don't think we have met? So hello!
Yeah, I Googled Tiger Tiger and realised that "simmer sauce" is what we call "curry paste".
Except it's not the paste, it's the sauce, all you add is the veggies or meat. I cook up the chicken and then add the sauce in to simmer for 20-30 minutes to allow the sauce to blend with the meat or veggies.
Look up Patak's brand of sauces for a better idea. Sorry about the link.
My choices for flavor are:
jalfrezi
korma
Madras
rogan josh
tikka masala
vindaloo
I tend to stick to the medium and mild curries. I have some curry powders, but using the sauces are quicker and makes two meals for me.