Warm the milk slightly (not hot) and mix with sugar and instant yeast in a large bowl. Let it sit 5 minutes until foamy.
Add flour, salt, egg, softened butter, and ground cardamom. Mix until dough forms.
Knead by hand for 10 minutes or with a mixer for 6–7 minutes until smooth and stretchy.
Place dough in a greased bowl, cover, and let rise 1–2 hours until doubled.
Mix filling: butter, brown sugar, and cardamom until smooth.
Roll risen dough into a rectangle (16x20 inches). Spread filling evenly.
Fold dough in half lengthwise. Roll lightly to flatten.
Cut into 1-inch strips. Twist each strip and tie into a knot.
Place knots on parchment-lined trays. Cover and let rise 30–40 minutes until puffy.
Bake at 375°F (190°C) for 12–15 minutes, until golden.
While warm, brush with simple syrup and sprinkle with cardamom sugar.