Lightly beat the egg and egg yolk together in a measuring cup. Add enough lukewarm water to make 1¼ cups total liquid. Set aside.

In a large bowl, sift together the flour and salt. Stir in the sugar and yeast. Add the diced butter and rub it into the flour mixture with your fingertips until it resembles breadcrumbs.

Make a well in the center of the flour and pour in the egg mixture. Stir with a wooden spoon until a dough forms, then knead by hand until it leaves the sides of the bowl.

Turn the dough out onto a lightly floured surface and knead for about 10 minutes, until smooth and elastic.

Lightly oil a clean bowl. Shape the dough into a ball, place it in the bowl, and cover with a damp towel or plastic wrap. Let rise in a warm place for 1–2 hours, until doubled in size.

Brush a 7½ x 4½ x 3½-inch loaf pan with oil. Punch down the dough and knead briefly for 1 minute. Shape into a rectangle the length of the pan, fold lengthwise into thirds, and place seam-side down in the pan.

Cover and let rise again for 30 minutes, or until the dough reaches the top of the pan.

Preheat the oven to 425°F (220°C). Bake for 30 minutes, until golden brown and the loaf sounds hollow when tapped on the bottom.

Turn the bread out onto a wire rack and allow to cool before slicing.