To begin, place your sourdough starter in a large bowl. Stir in lukewarm water using a wooden spoon until evenly mixed. Add molasses at this stage if using, stirring until fully dissolved for a richer depth of flavour.

Gradually add the rye flour and salt, mixing with a spoon or hands until a thick, sticky dough forms. Do not over knead, rye lacks gluten so the texture will remain tacky and dense. Ensure all flour is hydrated before proceeding.

Cover the bowl with a damp cloth or cling film and let the dough ferment at room temperature for 12 to 24 hours. Choose a warm and draft free area to encourage proper souring. Longer fermentation yields deeper flavour.

Once risen and slightly domed with visible bubbles, dust a work surface with rye flour. Turn out the dough and shape it into a round or oval loaf, handling gently to avoid deflating. Avoid kneading, shape with floured hands.

Line a baking sheet with parchment paper and sprinkle it with rye flour. Transfer the shaped loaf onto it. Cover loosely with a towel and let it rest for another 1 to 2 hours to allow the surface to dry slightly and form a skin.

Preheat your oven to 220°C. Place an empty metal tray on the bottom rack while preheating. This will be used to create steam, which helps develop a firm crust typical of traditional rye loaves.

Once ready to bake, score the top of the loaf with a wet serrated knife or razor blade to control cracking during baking. Traditional Finnish loaves often have a single, deep slash across the centre.

Place the loaf on the middle rack of the oven. Pour a cup of hot water into the preheated tray below to generate steam, then close the oven door quickly. Bake for 15 minutes at 220°C, then reduce heat to 190°C and bake for 35 more minutes.

Remove the bread and cool it fully on a wire rack before slicing. Serve with butter, smoked fish, or strong cheese. For best flavour and texture, allow the loaf to rest for several hours before cutting. Store wrapped in a cloth at room temperature.