01 - Combine flour, sugar, yeast, and salt in stand mixer bowl.
02 - Add eggs and lukewarm milk. Mix on low speed with dough hook until shaggy dough forms.
03 - Increase to medium speed, knead for 5 minutes. Gradually add softened butter cubes until fully incorporated and dough is smooth and elastic, approximately 10 minutes.
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 dough and roll 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 into log. Slice lengthwise down center to expose swirl. Twist two halves together, keeping cut sides facing up. Gently transfer to prepared pan.
09 - Cover and let rise until puffed, approximately 45 minutes.
10 - Preheat oven to 350°F.
11 - Whisk egg and milk for egg wash, brush evenly over loaf.
12 - Bake for 30 to 35 minutes until golden brown and loaf sounds hollow when tapped.
13 - Cool in pan for 10 minutes, then transfer to wire rack to cool completely before slicing.