Preheat oven to 375 and line 12 muffin cups with paper liners

Whisk together the wet ingredients: milk, egg, egg yolk, maple syrup, and vanilla.

Add melted, but cooled, butter and stir to combine.

In separate bowl: whisk flour, sugar, baking powder, and salt. Add the wet ingredient mixture to the dry ingredient mixture and stir gently.

Fold in blueberries.

Spoon batter into 12 muffin cups.

Bake until tops are golden, about 18 minutes.

While muffins are in the oven, make the maple glaze: in saucepan over low heat, stir maple syrup and lemon juice, bringing to a simmer. Cook like this, stirring occasionally, for 12 minutes.

Remove pan from heat and let cool slightly. The glaze will continue to thicken as it cools, but don't let it cool too much or it will be difficult to spread.

When the muffins are done, poke holes with toothpick and spoon glaze over the top of the muffin. Be careful not to pour a glaze that is too thin on the muffins otherwise it will run down the side of the muffin liner and make quite a mess! Just monitor the glaze carefully while it's cooling, until the desired thickness is reached.