Toast oats and barley together in a large pan over medium heat for 5–7 minutes, stirring frequently, until fragrant and lightly golden. Tip into a bowl and stir in cashews, sesame seeds, ginger, and salt.
Melt butter and chocolate together in a small pan over low heat, then stir in honey and vanilla.
Pour the chocolate mixture into the oat mixture and stir until everything is well coated and combined.
Press firmly into a lined 8x8 inch baking tin, using the back of a spoon or wet hands.
Refrigerate for at least 2 hours until set, then cut into 12–16 bars.
Store in an airtight container in the fridge for up to a week.