If using instant yeast – add the yeast, milk, and water (make sure the milk and the water are lukewarm in temperature) to a bowl and whisk to combine. Then add the rest of the ingredients (sugar, salt, butter, flour) and stir together with a wooden spoon. If the dough is very sticky, you can add more flour a little bit at a time. Once a dough starts to form, you can start kneading.
If using active dry yeast or fresh yeast – Heat up the milk and water, either in the microwave or in a saucepan, until it is “fingervarm” (finger warm), meaning it should feel warm to the touch but not hot. Add the yeast and stir to dissolve. Let it rest 5-10 minutes until it begins to froth and bubble a little bit. Then, add the rest of the ingredients (sugar, salt, butter, flour) and stir together with a wooden spoon. If the mixture seems very wet and sticky, you can add a little more flour a bit at a time. Once a dough starts to form, you can start kneading.
Knead for 10-12 minutes, either by hand or in a stand mixer, until the dough is smooth and elastic. If it sticks to your hands, add more flour.
Cover and let the dough proof for about 1 hour, or until doubled in size and passes the poke test (should NOT spring back immediately when poked, should spring back slightly but leave an indentation).
Oil a loaf pan (or line with parchment paper if you’re like us and your loaf pans are the opposite of non-stick).
To shape the sandwich loaf, dump the dough out on a clean surface. Using your hands, stretch it out into a rectangle, with a width equivalent to the size of your loaf pan.
Start rolling from one end, keeping the roll very tight.
Once you have rolled it up, pinch together the crease on the bottom, then flip the loaf so it's seam-side down and roll it against the countertop gently to create surface tension and help close the crease on the bottom of the loaf.
Place the loaf in the pan and cover, letting it rise for another 30-45 minutes, or until doubled in size and passes the poke test again. In the meantime, preheat your oven to 350 F (175 C).
Once it is ready to go in the oven, brush the top with a bit of milk and bake.
You can also score the top of the bread! This will give it a nice pattern on top, but it isn't required - the dough will still rise properly without scoring it.
Bake for 30-35 minutes (make sure to check it at 30!) until the top is golden brown and the bread sounds hollow when you tap it.
Let cool at least 20 minutes before slicing. Enjoy!