01 - In a large mixing bowl or stand mixer fitted with a dough hook, combine the flour, sugar, yeast, and salt. Whisk the warm milk and egg together, then pour into the dry ingredients. Mix until a shaggy dough forms, then add the softened butter. Knead for 8–10 minutes until the dough is smooth, elastic, and slightly tacky. Cover the bowl with a damp towel or plastic wrap and let rise in a warm spot for 1 hour, or until doubled in bulk.
02 - Place the room-temperature butter between two sheets of parchment paper and roll it into a rectangle approximately 8×10 inches. Transfer to the refrigerator and chill until firm yet still pliable, about 15–20 minutes.
03 - On a lightly floured surface, roll the risen dough into a large rectangle roughly 16×12 inches. Lay the chilled butter block over one half of the dough, then fold the other half over to enclose the butter. Roll out gently to seal, then fold the dough into thirds like a letter. Wrap in plastic and refrigerate for 20 minutes. Repeat this rolling and folding process two more times, chilling 20 minutes between each turn, for a total of three folds.
04 - Roll the laminated dough out once more into a 16×12-inch rectangle. Trim the edges with a sharp knife or pizza cutter for clean, even lines. Cut the dough into 12 equal strips, each about 1 ¼ inches wide. If using a filling, spread a thin, even layer of chocolate spread, jam, or your chosen filling over each strip.
05 - Roll each strip tightly from one end to the other into a compact spiral. Using a sharp knife, slice each spiral in half lengthwise to expose the layered interior. Twist each half into a loose knot and place it cut-side up into a generously greased 12-cavity muffin tin.
06 - Cover the muffin tin loosely with a damp towel or oiled plastic wrap. Let the shaped cruffins rise in a warm, draft-free area for 45–60 minutes until visibly puffed and nearly doubled in size.
07 - Preheat the oven to 390°F (200°C). Bake the cruffins on the center rack for 20–25 minutes, rotating the tin halfway through, until the tops are a deep golden brown and the layers have pulled apart slightly. Remove from the oven and let cool in the tin for 3–4 minutes.
08 - While still warm, brush the cruffins with melted butter and roll them in the cinnamon-sugar mixture if desired. Transfer to a wire cooling rack. Serve as-is, or use a piping bag fitted with a long nozzle to inject lemon curd, Nutella, or pastry cream directly into the centers for an extra-indulgent treat.