Preheat your oven to 155°C (311°F), fan/convection setting on if available (see Note 1 below if your oven doesn't have this function). Line a 12-cup cupcake tray with liners.
In a mixing bowl, whisk together the flour, sugar, cocoa powder, baking soda, and salt until fully combined. Set aside.
In a heatproof bowl, combine the dark chocolate and vegetable oil. Microwave in short bursts (about 1 minute total) until the chocolate is melted, then stir until smooth and glossy.
Add the yogurt, eggs, vanilla extract, and instant coffee powder to the melted chocolate mixture. Whisk until well combined and slightly thickened.
Pour in the hot water and mix until fully incorporated.
Add the wet mixture to the dry ingredients and whisk for about 45 seconds, just until combined. Avoid overmixing — this keeps the crumb soft rather than dense.
Divide the batter evenly between the cupcake liners, filling each about two-thirds full.
Bake for 18–20 minutes, or until a toothpick inserted into the center comes out clean.
Let the cupcakes cool completely in the tray before frosting. Chocolate Swiss meringue buttercream pairs beautifully with these.