Cook strawberries and sugar in a small saucepan over medium heat for 10 minutes or until the sugar is completely melted and the strawberries begin to break down. Mash with a potato masher.
In a medium bowl whisk the egg yolks.
Strain the strawberry syrup slowly into the egg yolks while mixing.
Add back to the saucepan. Cook until thickened. Stir in the butter.
Cool to room temperature and then transfer to mason jars or a glass bowl.
Chill for at least 3-4 hours.
Notes
Frozen strawberries may be subbed in for fresh berries if desired.