Heat oven to 350°F. Line an 8-inch square pan with parchment, leaving overhang.
Melt butter and the 6 oz chopped semisweet chocolate in a heatproof bowl set over barely simmering water. Stir until smooth, then cool 5 minutes.
Whisk in granulated and brown sugars until glossy and combined.
Beat in eggs one at a time until the batter looks thick and shiny. Stir in vanilla and kirsch.
Whisk flour, cocoa, salt, and espresso powder in a separate bowl.
Fold dry ingredients into the chocolate mixture just until no dry streaks remain.
Fold in chopped cherries and chocolate chips. Do not overmix.
Spread half the batter in the pan. Spoon small dollops of cherry preserves over it and gently swirl. Cover with remaining batter and lightly swirl again.
Bake 28–32 minutes, until edges are set and a tester comes out with moist crumbs. Cool completely in the pan.
Warm cream in a small saucepan until steaming. Pour over the 6 oz finely chopped bittersweet chocolate, rest 2 minutes, then whisk smooth.
Spread ganache over cooled brownies. Let set 20–30 minutes until just firm.
Lift out using parchment and slice into 16 squares.