Combine the sweetened condensed milk, espresso, butter, and vanilla extract in a saucepan over low heat. Whisk until combined and warmed through.

Slowly sift the powdered sugar into the sauce pan, whisking as you incorporate, until all the sugar has been added. Continue simmering, for about 5 minutes, whisking regularly. Turn off the heat.

Transfer to the fridge for 30 minutes to allow the glaze to thicken. Note: The glaze should be very thick and viscous. Continue to chill the glaze until it sets up and reaches the correct consistency.

Preheat oven to 400ºF.

Sift the all-purpose flour into a large mixing bowl. Add the sugar, baking soda, baking powder, ground cinnamon, salt, and instant coffee granules and stir to incorporate.

In a medium mixing bowl, add the chilled espresso, two eggs, milk, vanilla extract, and maple syrup. Use an electric mixer to whisk until combined.

Pour the wet ingredients into the dry ingredients and use the electric mixer to beat until combined. The batter should be a very thick but still maintain a liquid consistency.

Pour the batter into a 4-cup liquid measuring cup with a spout. This will make it easier to pour the batter into the muffin tins.

Place muffin liners in a muffin tin. Pour the batter into the liners, filling the liner up 3/4 of the way.

Transfer to the oven and bake for 20-22 minutes or until a toothpick comes out clean.

Remove from the oven and transfer to a wire baking rake to cool.

Place the Vietnamese iced coffee muffins on a plate or baking sheet and drizzle with the sweetened condensed milk glaze. Reserve any excess glaze for another use. Enjoy!