Bread Basket Pt.3 Egg whites in soft doughs

This is a test of two identical soft bun doughs. The only difference between the two is that one has egg whites substituted for the water. The white is around 90% water by weight anyway, so this substitution doesn't require much manipulation of the rest of the recipe.
Bun #1
100g bread flour
18g butter, room temperature
3g salt
3g yeast
40g water, at 40F
18g egg yolk
Bun #2

100g bread flour

18g butter, room temperature

3g salt

3g yeast

42g egg whites

18g egg yolk

Method for both buns:

Mix the salt, yeast, egg, water, and butter together in a bowl. Add the flour all at once and knead until the dough is uniform. Ferment at room temperature for 3 hours, or once the dough doubles in size. Shape into buns and proof for 1 hour. Bake at 400F for 9 minutes, or until lightly brown, egg washing after 3 minutes.

The results were closer in texture than I would have expected. The top bun in this picture has no egg whites.

Even though there wasn't a huge difference, I definitely preferred the bun without the whites. The whites make the crumb chewier, kind of waxy.

Plate it up!

Butter poached lamb flap with cilantro mayo, purslane, pickled daikon, pickled carrot, and chicken liver mousse on a soft, egg yolk only, bun.

There may  be too much fat in these, so much it is preventing the interior from being fluffy. I'll be looking for a lighter, fluffier sandwich bun.

Forcefully,

Adam