In a large mixing bowl, combine softened unsalted butter, oil, light brown sugar, and honey using an electric mixer on medium speed. Beat until smooth and creamy, about 1 minute.

Add in the egg and vanilla extract, mixing on low speed until just incorporated.

Gradually sift in all-purpose flour, baking soda, salt, and cinnamon. Mix on low until just blended, ensuring no flour streaks remain.

Transfer the dough to a covered container or wrap it tightly in plastic wrap, then refrigerate for about 1.5 hours until firm.

Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.

Scoop out large portions of dough (about 3 tablespoons each) and roll them into balls, placing them on the prepared baking sheet.

Bake for around 10 minutes, or until the edges are set and just beginning to brown.

Immediately sprinkle the tops with fleur de sel after removing from the oven. Allow to set for a few minutes before transferring to a wire rack.

Let the cookies cool slightly before serving.