Activate Yeast (5 min): In a stand-mixer bowl, whisk warm buttermilk, warm water, yeast, and sugar. Cover; rest 5 minutes until lightly foamy.

Mix Dough (2–3 min): Add melted butter, egg, salt, garlic powder, and 1 cup flour. Mix on low 30 seconds; scrape. Add remaining flour; mix on low ~2 minutes until a shaggy dough forms.

Knead (5 min): Knead with dough hook 5 minutes (or by hand). Dough should be soft and slightly tacky, not sticky. Sprinkle in flour 1 tsp at a time only if needed. Readiness: dough slowly springs back when poked; a thin “windowpane” stretches without tearing.

First Rise (1½–2 hrs): Lightly oil a large bowl. Add dough, turn to coat, cover, and let rise in a warm spot until doubled.

Prep Pan: Grease a 9×5-inch loaf pan (parchment sling optional).

Fill & Twist: Punch down dough. On a lightly floured surface, roll to ~9×15 in. Sprinkle cheddar evenly, leaving a ½-in border. Roll up tightly (15-in log), seam down. Split lengthwise; cross the halves to form an “X” and twist tightly. Pinch ends and place in pan.

Second Rest & Preheat (30 min): Cover; rest 30 minutes to puff slightly. Position oven rack to lower third; place a baking sheet on the rack below. Preheat to 350°F (177°C).

Garlic-Herb Butter: Mix melted butter, parsley, and garlic powder. Brush over dough (reserve a little for later if desired).

Bake (45–55 min): Bake until deep golden and the top sounds hollow when tapped (tent with foil if browning too fast ~25 min). Cool 10 minutes in pan, then transfer to a rack to cool further.

Slice & Serve: Slice with a serrated knife. Serve warm; rewarm slices 10 seconds in the microwave to re-melt cheese.