Preheat the oven to 350°F. Line 48 mini cupcake cups with mini cupcake liners. [Tip: Depending on how the batter is divided you may be able to yield more than 48 so have extra liners on hand.]
In a microwave safe bowl, melt together the chocolate and butter. Melt on high for 1 minute, then stop and stir. Repeat until smooth.
To the melted chocolate add the sugar, eggs, espresso and vanilla. Mix until combined. Whisk in the all-purpose flour and salt mixing until fully combined.
Divide the batter between the mini muffin cups using a small ice cream, cookie scoop or teaspoon
Bake for 18-20 minutes or until a toothpick inserted into the center shows moist crumbs.
Remove from the oven and top each with a candy kiss. Cool in the pan for 5-10 minutes to allow the candy to melt slightly then move onto a cooling rack to cool completely.