Use a sharp vegetable peeler to remove only the bright yellow outer layer of the lemons, avoiding as much white pith as possible since it introduces harsh bitterness. Work slowly and rotate the fruit as you peel to create wide strips with maximum aromatic surface area.

Place the lemon peels in a bowl or jar and add the sugar directly on top. Use clean hands or a muddler to gently massage and press the peels into the sugar until they become glossy and slightly softened. Cover and let sit at room temperature for 4–12 hours, stirring once or twice during this time until the sugar fully dissolves into a thick citrus oil syrup.

Once the syrup looks wet, translucent, and intensely fragrant, strain out the lemon peels using a fine sieve, pressing lightly to extract the last aromatic oils without forcing bitter compounds. Transfer the finished oleo saccharum to a sealed jar and refrigerate until ready to use.

In a large chilled pitcher, combine the measured oleo saccharum syrup, fresh lemon juice, and a pinch of fine sea salt. Stir slowly until fully dissolved and taste the mixture; it should feel intensely lemony but structured, with sweetness supporting the citrus rather than dominating.

Fill the pitcher generously with ice just before serving, then pour in the chilled club soda. Stir gently only once or twice to integrate the base without flattening the bubbles or over-diluting the drink.

Pour the spritz into ice-filled glasses, garnish each with a fresh lemon peel twist and optional thyme sprig for aromatic lift, and serve immediately while fully cold, bright, and sparkling.