Prepare the base: In a saucepan, combine rhubarb, sugar, honey (or corn syrup), lemon juice, and lemon zest.
Cook until the rhubarb breaks down: Place over medium heat and simmer until the mixture is completely broken down, about 10–15 minutes.
Purée to smooth thickness: Mash or blend until the mixture is smooth and thick.
Thicken with a starch slurry: Whisk the cornstarch with water to form a smooth slurry, then stir it into the rhubarb mixture.
Cook until very thick: Continue cooking, stirring, until the mixture becomes very thick and paste-like.
Add richness: Remove from heat, then stir in the butter and a pinch of salt until melted and well incorporated.
Shape the logs: Spread the mixture onto a lined tray, aiming for a thickness of about 1–1.5 cm. Let it cool completely.
Cut into logs: Once cool, cut into strips or roll into logs.
Dry to chewy perfection: Leave the logs uncovered for a few hours (or overnight) to dry slightly and achieve chewiness.
