Line a lipped baking tray with lightly greased baking paper.
Mix together the sugar, corn syrup and water in a heavy-based saucepan and heat over a low heat until the sugar dissolves. Stir occasionally to help it along
Then Increase the heat slightly and cook until the mixture begins to become golden in color (25 minutes for me, and a thermometer reading of 320 degrees F/ 160 degrees C),
Quickly mix in the butter, cardamom, and saffron liquid before cooking for another 3-4 minutes until it changes to an even butterscotch color (my thermometer read 257 degrees F/ 125 degrees C).
Transfer the cardamom pistachio butter toffee mixture onto the lined baking tray and use a spatula to smooth it out as thinly. If there is a layer of still liquid butter on top, then just pour it all away.
Sprinkle on the pistachios and half the rose petals and press them gently into the surface of the toffee.
Cool the toffee completely, cut into pieces with a sharp knife or scissors, sprinkle on the rest of the rose petals and serve.
Notes
Invest in a good-quality candy thermometer to ensure precise temperature control, especially when working with sugar for the toffee.
When adding butter, cardamom, and saffron liquid, work quickly to incorporate them into the toffee mixture. This step requires efficiency to achieve the desired consistency.
Pay close attention to the color changes during cooking. Achieving a golden brown color in the initial stage and an even butterscotch color later are crucial for the toffee's flavor and texture.
Use a sharp knife or scissors to cut the homemade toffee into pieces.
Adapted from Cardamom–pistachio butter fudge, Saraban by Greg and Lucy Malouf.