01 - Preheat oven to 350°F. Line an 8-inch square baking pan with parchment paper, leaving overhang on two sides for easy removal.
02 - Combine the butter and chopped dark chocolate in a heatproof bowl set over a saucepan of barely simmering water. Stir gently until completely smooth and glossy. Remove from heat and let cool slightly for about 5 minutes.
03 - Whisk the sugar into the melted chocolate mixture until well blended. Add eggs one at a time, beating well after each addition. Stir in the vanilla extract until the batter is silky and uniform.
04 - Gently fold the flour and salt into the batter using a spatula, mixing only until just combined. Avoid overmixing to maintain a tender, fudgy crumb.
05 - Pour the batter into the prepared pan and spread it into an even layer. Bake for 25 to 30 minutes, or until a toothpick inserted into the center comes out with moist crumbs clinging to it. Do not overbake. Allow the brownies to cool completely in the pan on a wire rack.
06 - Once the brownie base has cooled completely, arrange the sliced strawberries in a single even layer across the entire surface, pressing them down gently so they adhere.
07 - Place the semisweet chocolate and coconut oil (or butter) in a clean heatproof bowl over simmering water. Stir until melted, smooth, and pourable.
08 - Pour the melted chocolate over the strawberry layer, spreading gently with a spatula to cover the surface evenly. Refrigerate the pan for at least 1 hour, or until the chocolate shell is fully set and firm to the touch.
09 - Lift the brownies out of the pan using the parchment paper overhang. Run a sharp knife under hot water, dry it, and cut into 12 squares for clean edges. Serve chilled or at room temperature.