Preheat the oven to 350°F (175°C). Grease a 9x13 inch baking dish and line with parchment for easy removal.

In a small saucepan, melt the butter over low heat. Stir in the granulated sugar until evenly mixed and let cool for 1–2 minutes.

Whisk the eggs and vanilla into the butter-sugar mix until smooth and slightly glossy.

Sift or whisk together the flour, cocoa powder, salt, and baking powder. Fold in the dry ingredients into the wet mixture until just combined.

Spread the batter into the prepared pan and smooth the top with a spatula.

Bake for 20 to 25 minutes. The edges should be set and a toothpick inserted should come out with a few moist crumbs.

Remove from oven and cool completely on a wire rack. Once cooled, set the chopped chocolate and vegetable oil in a heatproof bowl over gently simmering water.

Stir until smooth and glossy, or alternatively, microwave in 20-second bursts, stirring between.

Cut the cooled brownies into bars and dip each into the melted chocolate, tapping off excess.

Let the chocolate set at room temperature until firm or chill briefly to speed up setting.