Munchmallow Cupcakes

Name: Munchmallow Cupcakes
Ingredients: 1½ cups (113 g) unsalted butter, room temperature, plus a bit more for pans; ¾ cup (80 g) cocoa powder, plus a bit more for pans; ¾ cup (180 ml) hot water; ¾ cup (180 g) sour cream; 1⅞ cups (200 g) all purpose flour, sifted; 1 tsp baking soda; ½ tsp salt; 1 tsp vanilla extract; 4 eggs; 1⅛ cup sugar; 3 egg whites; ½ tsp cream of tartar (if you don’t have cream of tartar, use ½ tsp salt); 1 tbsp vanilla extract; ¼ cup (60 ml) water; 1¼ cup (280 g) sugar; 10.5 oz (300 g) dark high quality chocolate; 4 tbsp sunflower oil