Preheat oven to 350°F (175°C). Line an 8x8-inch pan with parchment paper leaving an overhang and grease the paper lightly with nonstick spray or butter.

Melt the butter and chopped bittersweet chocolate together until smooth; cool slightly.

Stir granulated sugar and light brown sugar into the warm chocolate mixture until mostly dissolved.

Add eggs one at a time, whisking until glossy after each addition; stir in vanilla and optional espresso powder.

Sift flour, cocoa powder, and salt; fold into the chocolate mixture until just combined.

Pour batter into the prepared pan, smooth the top, and bake 22–28 minutes until edges are set and a toothpick comes out with moist crumbs.

Cool the brownies completely in the pan, then chill 30–45 minutes to firm before glazing and slicing.

Make sugared cranberries: dissolve 1/2 cup sugar with 2 tablespoons water to make simple syrup; coat cranberries in the syrup and then roll in extra granulated sugar. Let dry on a rack for at least 30 minutes.

Heat heavy cream until just simmering and pour over chopped dark chocolate; let stand, then stir until smooth. Stir in 1 tablespoon butter and a pinch of kosher salt if using. Cool until slightly thickened but still pourable.

Melt the white chocolate or candy melts until smooth; if needed, thin with a teaspoon of neutral oil. Transfer to a piping bag and snip a small corner.

Remove chilled brownies from the pan, place on a wire rack and pour the cooled chocolate glaze over the top, spreading to the edges. Allow glaze to set slightly.

Pipe thin lines of white chocolate across the glazed surface and, if desired, drag a small spatula perpendicular to create a ribbon effect.

Using a sharp knife, cut brownies into 16 squares, wipe the knife between cuts for clean edges. Top each square with sugared cranberries and a small rosemary sprig; dust with powdered sugar and optional sanding sugar.

Package as desired in boxes layered with parchment, keep chilled until giving, and allow refrigerated squares 20–30 minutes at room temperature before serving for best texture.