Preheat oven to 350°. Prepare a 12 cup muffin pan. Either line with muffin papers or spray with cooking spray.
In a liquid measuring cup, melt ½ cup of butter. Allow butter to cool while you combine the dry ingredients.
In a large mixing bowl, combine flour, sugar, baking powder, baking soda, salt, and lemon zest. Stir to combine.
To the melted butter, add Crème fraîche, egg and egg yolk, buttermilk, vanilla, and lemon juice. Whisk to combine.
Combine the wet and dry ingredients. Mix gently until the batter is just combined. Be careful not to over-mix. Fold in the chocolate chips.
Divide the batter evenly between the muffin cups. I like to use a cookie scoop for this part. Bake at 350° for 20-22 minutes. Remove from the oven and allow to cool.
In a small sauce pan, combine lemon juice and granulated sugar. Which over medium heat until the sugar is completely dissolved. Remove from heat.
Transfer the muffins to a cooling rack. Set up parchment paper underneath the cooling rack. Drizzle the lemon glaze over the cooled muffins. Allow the glaze to set up for 30-45 minutes before serving.
These muffins are best enjoyed the day that they are made. You can store leftover muffins in an airtight container for 1-2 additional days. For this recipe, you will want to use fresh lemons and lemon juice.I have a special tool which is used for zesting citrus. You can also use a microplane cheese grater for zesting the lemons. Link to lemon zester is at the bottom of the post.