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