Mix the dough: Combine all ingredients except fat in the bowl of a stand mixer fit with the dough hook. Mix on medium-low until smooth, about 7 minutes. Cover the bowl and rest the dough for 5 minutes.

With the mixer on low, add the fat about a third at a time, waiting until each portion is incorporated before adding the next. Once all the fat has been added, mix on medium-low until dough is very smooth and passes the windowpane test, about 5 minutes.

Bulk proof: Transfer the dough to a clean and lightly oiled container. Cover and bulk ferment until noticeably risen, though not doubled (in my low-70s environment, about 90 minutes).

Divide and shape: Divide the dough into 4 equal pieces and preshape gently into rounds. To shape the sandwich loaf, take one round and place it smooth side down on a clean work surface. Roll the dough into a rectangle roughly 4”x14”, aiming to degas the dough well. Fold the two long edges to the center, slightly overlapping. Roll back into a rectangle about 4”x14”, again doing your best to fully degas the dough, then roll up tightly like a jelly roll. Pinch seam to seal. Repeat with other three portions.

Final proof: Transfer rolls to a lightly greased 13x4 pullman pan, seam sides down. Mist the surface with oil and cover loosely with plastic. Allow to rise at room temperature until dough roughly triples in volume and just reaches the top of the tin (in my low-70s environment, 2.5-3 hours).

Preheat and bake: About 30 minutes before baking, preheat oven to 400F with a rack in the middle. After the dough has finished proofing, brush the top lightly with milk, transfer to oven, and bake for 20 minutes. After 20 minutes, reduce the heat to 350F and continue baking for 15-20 minutes, or until the internal temperature is at least 195F. If the loaf is browning too quickly, tent a piece of foil over the top to keep from burning.

When the loaf is finished, immediately remove from the pan and turn onto a wire rack. Brush melted butter over the top and sides while the loaf is still warm, if desired. Allow to cool completely before slicing. Store leftovers in a sealed plastic bag.