In a big bowl or stand mixer, add yeast*, sugar, warm water, oil and egg. Mix to incorporate. Add mash, salt and flour. Start with less flour (about 3 cups to begin) as the temperature of your house will affect the dough. Knead in a stand mixer for 5 min or by hand for 10, adding flour as needed, until you have a homogenous, supple dough ball.*See note below for difference between Instant yeast and Active dry yeast Grease a big glass bowl with neutral oil and plop the dough ball in. Make sure the dough is totally coated in the oil. Cover with plastic wrap and/or a lint-free kitchen towel and let proof until doubled in size. Depending on the temperature in your house this could take up to two hours (the warmer your home, the quicker it will rise as the optimal temperature for yeast to thrive in your dough is about 80F. So for me, in South Florida, this step takes about 30 or 40 minutes)
After it's doubled in volume, shape your loaf on a floured surface. Make sure it is the same size as your loaf pan.
Score the top with a sharp knife or bread razor and cover again. Preheat your oven to 375F. Once the loaf has doubled, bake for 25 minutes. Cover with foil if the top gets too brown and bake another 15 min.
To make sure your bread is done baking, give it a knock. It should sound hollow when tapped on when it's done. It should be a deep golden brown like bread you buy from the grocery store.
Let cool overnight if possible. The steam trapped in the bread needs to be released slowly so the crumb texture can set up properly. If the steam escapes too quickly, the bread texture can come out doughy or squishy with an almost “wet” crumb even though the bread was cooked through. This is comparable to not letting meat rest before you slice into it. All of the juices rush out and the meat isn't as tender and juicy as it would be if you had let it rest for a bit! Make sense?
As tempting as it is to cut into a warm loaf of bread, keep this in mind! (I usually cut off the end piece after 20 min resting or so to satiate my warm-bread-eating-desires, but then I leave the rest to be sliced in the morning) Absolute minimum wait time to slice the whole loaf would be 1 hour in my humble opinion but you're the ruler of your kitchen so I give you the info and you do what you gotta do, boo!