Warm milk and butter until butter melts; cool until pleasantly warm.
Sprinkle yeast and 1 teaspoon sugar over warm milk; let foam 5–10 minutes.
Whisk flour, remaining sugar, cardamom, and salt in a large bowl.
Pour yeast mixture into dry ingredients; mix until a shaggy dough forms.
Knead until smooth and elastic, 8–10 minutes. Cover and rise until doubled.
Stir filling ingredients together until creamy and spreadable.
Punch down dough. Roll into a 12x18-inch rectangle on a floured surface.
Spread filling evenly. Fold in thirds like a letter; roll lightly to seal.
Cut into 12 strips. Twist each and tie into a loose knot.
Set on lined sheets. Cover and rise until puffy, 25–35 minutes. Preheat to 400°F.
Bake until deep golden and set, about 14–18 minutes.
Simmer sugar and water until clear. Brush hot buns; sprinkle coarse sugar. Cool 10 minutes.
Notes
Try adding a touch of orange zest to the filling for a citrusy twist. Store cooled buns airtight at room temperature for 2 days, or freeze up to 2 months; refresh in a warm oven before serving.This recipe is an original creation inspired by classic Easy Swedish Cardamom Buns flavors. All ingredient ratios and instructions are independently developed.