Chef John's Chocolate Lava Cake

Generously butter the inside of 4 (5 1/2 ounce) ramekins. Place them in a casserole dish.

Whisk together egg yolks eggs and sugar in a bowl until light foamy and lemon colored.

Melt chocolate and butter in a microwave-safe bowl in 30-second intervals stirring after each melting 1 to 3 minutes.

Stir melted chocolate mixture into egg and sugar mixture until combined.

Sift cocoa powder into the mixture; stir to combine.

Sift flour and salt into the mixture; stir to combine into a batter.

Stir vanilla extract into the batter.

Transfer batter to a resealable plastic bag. Snip one corner of the bag with scissors to create a tip.

Divide batter evenly between the prepared ramekins; tap gently on the counter to remove any air bubbles.

Refrigerate 30 minutes.