Add the butter to a frying pan or skillet over medium-low heat. Once melted, add the graham cracker pieces in a single layer, and toast for 2–4 minutes, per side until fragrant, golden, and lightly toasted.
Warm the half & half in a separate saucepan on the stove. The half & half should feel warm, not hot to the touch.
Add the toasted graham cracker pieces into the warmed half & half and gently stir to combine, being careful not to break up the graham crackers. Scrape any remaining melted butter from the saucepan into the half & half using a rubber spatula.
Allow the mixture to steep at room temperature for 15 minutes to infuse the graham cracker flavor into the dairy.
Strain the mixture through a fine mesh strainer to remove the graham cracker pieces.
Add the infused mixture to a blender along with the sweetened condensed milk, cocoa powder, honey, marshmallow extract, vanilla extract, salt, and cinnamon.
Blend until smooth and creamy.
Pour the creamer into a mason jar or creamer bottle and store in the refrigerator for up to 2 weeks or until the best by date of your half & half. Shake well before using.