Step 1: Preheat your oven to 180°C (350°F) to ensure even baking.
Step 2: Line a square baking pan (approximately 9x9 inches) with parchment paper, leaving some overhang for easy removal.
Step 3: In a heatproof bowl, melt the dark chocolate until it is warm and smooth; do not overheat.
Step 4: In a large mixing bowl, cream together the butter and sugar until light and fluffy.
Step 5: Add the eggs one at a time, mixing well after each addition.
Step 6: Dissolve the instant coffee in a tablespoon of hot water and stir it into the mixture.
Step 7: In a separate bowl, whisk together the flour, baking powder, and salt, then gradually add to the wet ingredients.
Step 8: Fold in the melted chocolate and chocolate chips gently, being careful not to overmix.
Step 9: Pour the batter into the prepared pan and smooth the top. Bake for 25-30 minutes until a toothpick comes out with a few moist crumbs.
Step 10: Cool in the pan for 10 minutes, then lift out using the parchment paper and cool completely on a wire rack before cutting into squares.