Preheat oven to 325°F (165°C) and line an 8x8-inch pan with parchment paper. Melt the 115g butter and 170g chocolate chips together over a double boiler, stirring until smooth, about 3 to 4 minutes. Cool for 5 minutes.

Whisk the 200g granulated sugar into the chocolate mixture, then add the 2 eggs one at a time, whisking well after each. Stir in the 1 tsp vanilla extract and whisk for 1 full minute until the batter is slightly thickened and glossy.

Fold in the 65g flour, 30g cocoa powder, 1/2 tsp salt, and 1/4 tsp baking powder with a spatula until just combined, about 20 to 25 folds.

Spread the batter evenly in the prepared pan and bake for 28 to 32 minutes, until edges are set and a toothpick inserted 1 inch from the center comes out with moist crumbs.

Cool in the pan for 20 minutes, then lift out using the parchment, slice into 9 squares with a clean knife, and serve crinkled-side up.