How to Make Chocolate Soufflé

Use this thorough recipe to make fluffy, yet rich chocolate soufflés

4 Tablespoons (1/4 cup; 56g) unsalted butter, cut into 4 Tablespoon size pieces
4 ounce (113g) semi-sweet chocolate bar, coarsely chopped*
3 large eggs, separated*
1 teaspoon pure vanilla extract
1/8 teaspoon salt
1/8 teaspoon cream of tartar
3 Tablespoons (38g) granulated sugar

1 Tablespoon (14g) unsalted butter, extra soft (the softer it is, the easier it is to spread)
4 teaspoons (16g) granulated sugar

For the batter: Melt the 4 Tablespoons of butter and the chopped chocolate together in a double boiler or in a large heatproof bowl in the microwave. Microwave in 20 second increments, stirring after each until completely melted and combined. Slightly cool for 3-5 minutes.
Whisk egg yolks, vanilla extract, and salt into chocolate mixture. Set aside.
In a completely clean residue-free medium glass or metal mixing bowl, using a handheld mixer or stand mixer fitted with a whisk attachment, beat the egg whites and cream of tartar together on high speed until soft peaks form, about 2 minutes. With the mixer running on high speed, slowly add the sugar in 3 additions about 1 Tablespoon at a time, beating for 5 seconds before adding the next Tablespoon. After all 3 Tablespoons of sugar have been added, beat until stiff
glossy peaks form, about 2 more minutes. Do not over-beat.
Slowly and gently fold the egg whites into the chocolate mixture. It’s best to do this in 3 separate additions, combining each addition completely before folding in more.