Trim and de-seed the red peppers, then roughly chop them into pieces. Put them in a blender (or food processor) and blend/ process them till very finely chopped. I would suggest adding about a 1/4 cup water to the chopped peppers for a more homogenous mixture. Blend/ process till fine, not to a paste.

Pour this into a largish thick walled heavy pot. I find my stoneware pots perfect for this. Mix in the garlic paste, chilli flakes brown and granulated sugars (adjust to taste), cider vinegar and salt. Bring to a boil and turn the heat down a bit. Let it continue to cook at a slow boil for about 10 minutes, stirring on and off.

Then turn down the heat a bit more and let the mixture simmer till it reduces and thickens, stirring frequently. It will start turning darker. Once it has reached desired consistency, mix in the butter.

Let it cool a bit and then transfer to clean sterilized jars. Let it cool completely, then cover and refrigerate.