Preheat oven to 350°F (175°C) and line an 8×8-inch pan with parchment paper.
Melt butter and chocolate together until smooth; cool slightly.
Whisk in both sugars, then eggs one at a time, followed by vanilla.
Fold in flour, cocoa, and salt until just combined.
Spread two-thirds of batter in the pan.
Warm caramel, mix with cream if needed, and drizzle over batter. Sprinkle crushed pretzels on top.
Drop remaining batter in spoonfuls and gently swirl with a knife.
Bake 28–32 minutes, until edges are set but center is slightly soft.
Cool completely before slicing.