In early spring (or any time of year thanks to frozen peas), sweet peas need very little else to create a light soup that highlights their fresh flavor. Pesto and asiago grilled cheese sandwiches are a rich and hearty complement to the light soup.
Heat a Dutch oven or large sauce pan over medium-high heat. Add oil and then onions, cumin and a pinch of salt to heated oil. Saute until onions are tender, 2 to 3 minutes. Add stock and bring to a simmer. Add peas and pesto (the portion for the soup) and reduce heat to medium. Simmer until peas are warmed through, about 5 minutes.
While soup simmers, place a skillet over medium heat. Assemble grilled cheese sandwiches by buttering one side of each piece of bread. Place half the slices of bread buttered-side down in hot pan. Top with pesto, cheese and then add remaining bread, buttered-side up. Cook until bottom of bread is golden brown, ~3 minutes. Flip and cook on the other side until filling is completely melted, ~3 minutes more.
Add the first portion of crème fraiche to soup (reserve the second portion for serving) and blend with an immersion blender (or in batches in a standing blender) until smooth. Season with salt and pepper.
Serve soup with reserved crème fraiche and parsley on top. Enjoy with pesto and asiago toast on the side!