Prepare your spice mix and prepare and gather the other ingredients to have handy.
Heat butter in a large skillet over medium heat. Add onion and cook, stirring, until onion is softened and starting to colour, 3-4 minutes. Add the Spice Mix and cook, stirring, about 1 minute. Add the curry paste, tomato paste, brown sugar, garlic and ginger paste and cook, stirring, another 30 seconds or so. Add the crushed tomatoes to the pan and stir to combined. Lower heat and allow to simmer until it slightly reduces, about 5 minutes.
*If desired, you can use an immersion blender in the pan to puree the sauce at this point, if you prefer a smooth sauce.
Add the frozen shrimp to the pan and stir to combine. Allow to simmer until shrimp is thawed and warmed in the case of cooked shrimp (2-3 minutes), or until cooked through, for raw shrimp (4-5 minutes). *The frozen shrimp will add some moisture to the sauce, but if sauce seems too thick at any point, add a splash of water to the mix.
Add cream (or coconut milk/yogurt) and stir to combine. Add fenugreek leaves, if using and stir to combine. Taste sauce and season with salt and pepper as needed.
Serve garnished with chopped cilantro and with sliced cucumber and lime wedges or slices. If desired, add some basmati rice and/or Naan bread.
Notes
Be sure to read the notes above the Recipe Card, for substitution suggestions and cooking tips. You will also find Step-by-Step photos there, as well.