Prepare an ice-water bath. Whisk yolks, 2 tablespoons sugar, and salt in a medium bowl.
Meanwhile, bring milk, cream, vanilla, and remaining 2 tablespoons sugar to a boil in a medium saucepan. Remove from heat.
Gradually mix half the hot milk mixture into yolk mixture until just combined. Pour yolk-milk mixture into saucepan with remaining milk mixture. Cook over medium-low heat, stirring constantly with a wooden spoon, until thick enough to coat back of spoon and hold a line drawn by your finger, 5 to 7 minutes. Strain mixture through a fine sieve into a bowl. Place bowl in prepared ice-water bath, and let stand, stirring occasionally, until cool.