Preheat your oven to 400°F (200°C), cut the cherries in half, spread them onto a parchment-lined baking sheet, sprinkle with sugar, and roast for about 10 minutes.

Reduce the oven temperature to 325°F (160°C). Grease an 8x8 inch baking dish with butter or spray and line it with parchment paper.

In a medium bowl, sift together the all-purpose flour, Dutch process cocoa powder, cornstarch, and salt.

In a large bowl, beat together the granulated sugar, eggs, and egg yolk for about 5 minutes. Gradually add the melted butter, oil, and vanilla extract.

Fold the dry ingredients into the wet mixture, add half of the roasted cherries and chocolate chips, creating a rich batter.

Pour the batter into the prepared baking dish and bake for 40 to 50 minutes, ensuring edges set and a toothpick inserted comes out with moist crumbs.

Let the brownies cool completely in the pan, freeze for 15 minutes for cleaner cuts, then slice and top with remaining roasted cherries.