2 large russet potatoes (1½ pounds), peeled and halved crosswise
2 medium beets (1 pound), peeled and halved crosswise
2 medium cucumbers
2 medium tomatoes
1 medium red onion
20 slices whole-wheat bread
Sea salt and freshly ground black pepper
To make the Chutney, boil 1½ cups of water in a small saucepan. Add the peas and cook over medium-high heat until soft, 8 to 10 minutes. Drain and rinse with cold water.
Transfer the peas to a blender; add 1 cup of water plus the remaining Chutney ingredients. Blend until smooth, transfer to an airtight container, and refrigerate for 1 hour.
To make sandwiches, place the potatoes and beets in a large pot fitted with a steamer basket over 1 to 2 inches of water. (Don’t let the potatoes and beets touch each other if you want to keep the potatoes white.) Bring water to a simmer, cover pot, and steam for 20 to 25 minutes, until vegetables are tender when pierced with a fork, but not too soft. Set aside to cool completely.
Slice the potatoes, beets, cucumbers, tomatoes, and onion as thin as you can (ideally ⅛- to ¼-inch-thick rounds).
Spread Chutney on one side of 10 bread slices. Layer the vegetables on top, starting with the potatoes, then beets, cucumbers, onion, and tomatoes. Sprinkle with salt and pepper to taste. Spread Chutney on one side of the remaining bread slices, and top the sandwiches. Cut each sandwich into quarters before serving.