Preheat oven to 350℉. Line mini muffin tins with mini cupcake liners and set aside.
Melt the unsweetened chocolate in a heatproof bowl over simmering water and set aside to cool.
Cream ½ cup of the butter and slowly beat in sugar, beating until light and fluffy.
Add the eggs, one at a time, and 2 teaspoons of vanilla; mix well.
Add the chocolate and mix until combined.
Sift together the flour, baking soda and salt and add to chocolate mix. Mix on low speed for a few seconds until combined, and then continue mixing on medium for about 2 minutes.
Add 1 cup of ice water and on low speed mix, increasing speed to medium once all the water has been incorporated , continue beating for about a minute.
Using a tbsp or filling a pastry bag with batter, fill each muffin tin to approximately 2 thirds full. Bake for about 10 minutes, until toothpick inserted in centre comes out clean. Remove from oven and cool completely on cooking rack.