01 - In stand mixer bowl, combine flour, sugar, yeast, and salt. Mix briefly to blend.
02 - Add eggs and lukewarm milk. Mix on low speed with dough hook until shaggy dough forms.
03 - Increase to medium speed, knead 5 minutes. Gradually add softened butter cubes, waiting for each addition to incorporate before adding more. 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, about 1 to 1.5 hours.
05 - Line 9x5-inch loaf pan with parchment paper.
06 - Punch down risen dough. On lightly floured surface, roll into 10x16-inch rectangle.
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 lengthwise down center to expose swirl.
09 - Twist two halves together, keeping cut sides facing up. Gently transfer twist to prepared loaf pan.
10 - Cover and let rise until puffed, approximately 45 minutes.
11 - Preheat oven to 350°F.
12 - Whisk egg with milk for egg wash. Brush evenly over loaf.
13 - Bake 30 to 35 minutes until golden brown and loaf sounds hollow when tapped on bottom.
14 - Cool in pan 10 minutes, then transfer to wire rack to cool completely before slicing.