Maggie's Tip: When making any bread with walnuts in it, never omit the step of roasting them, as these nuts are almost always rancid when sold shelled.
Step 1: Preheat the oven to 220°C.
Step 2: Roast the walnuts on a baking tray for about 5 minutes, shaking the trays prevent the nuts from burning. If they are not fresh season's, rub the walnuts in a clean tea towel to remove the bitter skins. Allow to cool.
Step 3: Combine the yeast, castor sugar and warm water in a small bowl, then dissolve the yeast by mashing it with a fork and set aside for 5 - 10 minutes until frothy. Meanwhile, warm 250 millitres milk and set aside.
Step 4: Combine the flour, salt, walnut oil and walnuts in the bowl of an electric mixer fitted with a dough hook, then add the yeast mixture. Combine the warm milk and sour cream. With the mixer set on a slow speed, gradually mix the sour cream and milk into the flour to make a soft but not sloppy dough. Turn the dough out onto a floured surface and knead it gently for 8 minutes. Brush the mixing bowl with a little more walnut oil and return the dough. Roll the dough around the bowl to coat with the oil, then place a piece of plastic film loosely over the surface of the dough. Leave in a draught-free place until doubled in volume, 30 - 45 minutes.
Step 5: Turn the dough out onto a floured surface again and gently knead it for 2 minutes. Shape into two baguettes and leave to rise on a baking tray dusted with flour in a draught-free place for 10 - 15 minutes.
Step 6: Meanwhile, preheat the oven to 220°C. Mix the egg with one tablespoon milk and lightly brush this over the loaves. Bake for 10 minutes, then reduce the temperature to 180°C and bake for a further 15 minutes. Turn out onto a wire rack and allow to cool completely before cutting.