1. To make the dough, sprinkle the yeast over the warm water in a small bowl. Let stand 5 minutes, then stir to dissolve. Pour into a large bowl. Add the cream, sugar, vanilla, lemon zest, and salt. Separate one of the eggs, and cover and refrigerate the yolk. Add the egg white and 2 whole eggs to the bowl and whisk until combined with the other ingredients.

2. Stir in enough of the flour to make a soft, slightly sticky dough. Turn out onto a lightly floured work surface and knead for about 8 minutes, or until the dough is smooth and supple. (The dough can also be mixed and kneaded in a heavy-duty electric mixer.) Gather into a ball, place in an oiled bowl, and turn to coat the dough. Cover the bowl with plastic wrap. Let stand in a warm place about 1½ hours until doubled in volume.

3. Line a baking sheet with parchment paper. Punch the dough. Transfer to the work surface and knead in the raisins. Take two-thirds of the dough and make 3 long ropes, each about 16in (40cm) long. Braid them together and place on the baking sheet. Using your fingertips, press a gutter lengthwise down the center of the braid.

4. Beat together the reserved egg yolk and milk. Brush the gutter with a little of the egg mixture. Divide the remaining dough into 3 equal portions. Roll into thin ropes, about 14in (35cm) long and braid. Place the smaller braid into the gutter on the larger braid. Cover loosely with plastic wrap and let stand in a warm place about 40 minutes, until almost doubled in volume.

5. Preheat the oven to 350°F (180°C). Uncover and brush the loaf with the egg glaze. Bake about 35 minutes or until golden brown and the loaf sounds hollow when tapped on the bottom. Transfer to a wire rack and cool.