Lightly grease the baking tin with oil and line with parchment paper, leaving excess hanging over the edges.
Toast the sesame seeds in a dry, wide frying pan over a medium heat, tossing until evenly golden.
Remove and set aside.
Gently melt the sugar in a medium saucepan over a medium heat, occasionally swirling the pan but not stirring, until it turns amber in colour.
This will take 15-20 minutes.
Add the toasted sesame seeds and ginger, swirling the pan to mix them in, and let it bubble until rich and golden in colour (and reading 160°C on a sugar thermometer if you have one).
Working fast before it sets, pour the mixture into the lined tin and tip it into the corners.
Leave for about 2 minutes to set a little. Use a lightly oiled table knife to score the surface into 3 equal strips down the length and 10 across the width, making 30 rectangles, each about 2.5cm × 6cm. Leave to set for 15-20 minutes.
Then lift out, peel the paper off and snap into pieces along the score lines.