Citrus Blossom Cold Brew Tonic

Combine ground-coffee and 4 cups cold sparkling-water in a large glass jar or pitcher; stir to saturate the grounds fully.

Seal the container and refrigerate for 16 to 20 hours (overnight yields the most velvety result).

Strain the infusion through a fine-mesh strainer lined with cheesecloth into a clean vessel; discard grounds or repurpose for compost.

The resulting concentrate should be dark, smooth, and bracingly bold. Store refrigerated until ready to use.

Combine white-sugar and 1/4 cup water in a small saucepan over medium heat; stir until sugar dissolves completely, about 2 minutes.

Add orange-juice, lemon juice, and orange peel strips; bring to a gentle simmer for 5 minutes, until the syrup thickens slightly and turns a pale amber hue.

Remove from heat and steep for 10 minutes off the burner to let citrus oils bloom into the syrup.

Strain through a fine-mesh strainer into a heatproof jar; discard peels. Cool to room temperature, then seal and refrigerate for up to 2 weeks.

In a large glass pitcher, combine 1 cup cold brew concentrate with 3 tablespoons citrus blossom syrup; stir briskly to integrate.

Add honey and stir until fully dissolved; taste and adjust sweetness with additional syrup or honey, a pinch at a time.

Add tonic-water and 6 of the mint leaves; stir gently to preserve effervescence.

Fill four tall glasses with ice cubes; pour the tonic mixture evenly among them, leaving a 1-inch crown of space.

Garnish each glass with one orange slice, one lemon peel twist, one remaining mint leaf, and a single rosemary sprig.

Serve immediately with a bamboo stirrer so guests can swirl and release the botanicals before drinking.