Mix the yeast the milk in a large bowl or the bowl of a stand mixer and let stand 5 minutes for the yeast to "bloom".
Add to the bowl 1 cup of flour, mashed avocados, sugar and salt.
Mix well until ingredients have blended together. Then add the remaining flour and knead by hand or on low-medium speed in a stand mixer for about 8-10 minutes. The dough will be smooth and elastic and although it will appear sticky, it won't stick to your fingers.
Add the vegan butter and knead on medium-high speed or by hand until the butter is incorporated into the dough.
Place the dough in an oil-coated bowl. Cover with plastic wrap and place in a warm place for about 1 1/2 hours or until doubled.
Punch the dough down, then cover again and let rise for another 2 hours.
To shape the dough, divide it into four equal portions. Shape each portion into a smooth, oval ball.
Spray oil on the inside of a standard 9 X 5-inch loaf pan.
Place the four balls of dough touching each other inside the loaf pan.
Cover loosely with oiled plastic wrap or with a shower cap and let rise another hour or until the loaf fills the pan and mushrooms over it.
For a nice color, brush on some extra virgin olive oil mixed with salt.
Bake in a 375-degree oven for 30 minutes.
Place the loaf pan on a rack and let the bread cool about 20-30 minutes or until cool enough to handle. Unmold the bread from the pan by sliding a knife around the edges and turning upside town. It should release quite easily.
Continue cooling, right side up, until thoroughly cooled.