Preheat your oven to 350°F (175°C). Line your square baking pan with parchment paper for easy removal. Leave a little paper hanging over the edges to act as handles.

In a large bowl, whisk the melted butter and granulated sugar together. Mix them well until the texture looks smooth and shiny. This step ensures a crackly top on your brownies.

Whisk in the eggs one at a time. Add the vanilla extract and beat the mixture for about two minutes. The batter should look thick and pale before you add the dry ingredients.

Gently fold in the cocoa powder, flour, and salt using a rubber spatula. Do not overmix the batter at this stage. You want to keep the brownies fudgy, not cake-like.

Fold in the semi-sweet chocolate chips for extra richness. These chips will create little pockets of melted chocolate. They make every single bite taste much more indulgent and special.

Pour the chocolate batter into your prepared baking pan. Use your spatula to spread it evenly into the corners. The batter will be quite thick and very dark.

Press the sliced strawberries gently into the top of the batter. You can arrange them in rows or a random pattern. If using jam, swirl small dots of it between the berries.

Bake for 25 to 30 minutes in the center of the oven. A toothpick should come out with a few moist crumbs attached. Do not wait for it to be completely dry.

Let the brownies cool in the pan for at least 30 minutes. This is the hardest part, but it helps the fudge set. Lift them out using the parchment paper and slice.