01 - In a stand mixer bowl, combine flour, sugar, yeast, and salt. Add eggs and lukewarm milk. Mix on low speed with a dough hook until a shaggy dough forms.
02 - Increase speed to medium and knead for 5 minutes. Gradually add softened butter, a few cubes at a time, until fully incorporated and dough is smooth and elastic, approximately 10 minutes.
03 - Transfer dough to a lightly greased bowl, cover, and let rise in a warm place until doubled in size, about 1 to 1.5 hours.
04 - Line a 9x5-inch loaf pan with parchment paper.
05 - Punch down the dough and roll out on a lightly floured surface to a rectangle about 10x16 inches.
06 - Spread raspberry jam evenly over dough, leaving a 1/2-inch border. Sprinkle with crushed fresh raspberries if using.
07 - Starting from a long side, tightly roll up dough into a log. Slice the log lengthwise down the center to expose the swirl. Twist the two halves together, keeping cut sides facing up. Gently transfer the twist into the prepared loaf pan.
08 - Cover and let rise until puffed, about 45 minutes.
09 - Preheat oven to 350°F.
10 - Whisk egg and milk for egg wash, and brush over loaf.
11 - Bake for 30 to 35 minutes, or until golden brown and loaf sounds hollow when tapped.
12 - Cool in pan for 10 minutes, then transfer to a wire rack to cool completely before slicing.