*If you cannot source pea flour, simply grind dried split peas to a fine powder in a coffee grinder or high-powered blender. Be careful not to cold retard for an extended period, as the sourdough acidity will overpower the delicate pea flavor.
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Combine peas, milk, honey, pea flour, and matcha in a food processor until smooth green slurry forms.
Place pea slurry, starter, and softened butter in a large bowl. Add flour and mix with hands until sticky, shaggy mass forms. Cover with plastic and autolyze (let rest) at room temperature for about 20 minutes, allowing flours to fully hydrate.
Sprinkle salt over dough and work into dough until fully incorporated. Knead on clean counter for 5 to 7 minutes, until dough feels smooth and elastic.
Transfer to lightly oiled bowl and cover with plastic. Allow to bulk ferment at room temperature for about 5 hours, until almost doubled in size.
When dough feels puffy and has almost doubled in size, remove from bowl and place on lightly floured surface. Divide into 2 equal parts, patting each into rectangle measuring about 6 by 8 inches. Fold rectangles from top down, tucking each fold in tightly to create surface tension on loaves. Lightly tuck ends under and place into oiled pan, seam side down. Note: If kitchen is cold (less than 70 degrees) cover and allow to proof at room temperature for another 2 to 3 hours. You may then cover and retard shaped loaf in refrigerator for up to 8 hours before baking.
Preheat oven to 435 degrees.
Mix yolk with cream to make egg wash and apply wash using pastry brush. Score each loaf down middle to about ¼-inch deep with lame. Place in oven for about 35 to 40 minutes, or until top is deep brown. Cool completely before slicing. Note: If you have the luxury and patience, wait up to one day before slicing to allow the crumb to set.