Whisk together the flour and salt in a small bowl.

Microwave the butter and semisweet chocolate in a medium bowl at 50% power for 2 minutes, stirring often until melted and smooth.

Whisk in the sugar, followed by the eggs one at a time. Whisk in the vanilla.

Add the flour and use a silicone spatula to stir just until fully combined.

Cover with plastic wrap and refrigerate for at least 2 hours or up to 4 days.

Preheat the oven to 350F and line 2 baking sheets with parchment paper.

Shape the dough into 1 tablespoon size balls and roll the balls in granulated sugar.

Place balls 2 inches apart on the prepared baking sheet. Using your thumb or the back of a teaspoon, press a slight indention in the center of each ball. Take care not to press too far down. If the edges crack while making the indention, simply pinch them back together to smooth them out. Otherwise, the cracks are okay.

Bake one sheet at a time for 10-12 minutes, until edges of the cookies feel firm. The indentations will have puffed in the oven, so you’ll want to press them down again while the cookies are still warm. Repeat with the second sheet. Let cookies cool completely.

Microwave the semisweet chocolate and oil in a medium bowl at 50% power for 2 minutes, stirring often until melted and smooth.

Use a spoon or piping bag to fill each indentation to the brim. Place cookies in the refrigerator for 10 minutes, until the chocolate is set.