Heat olive oil in a large pot over medium heat.
Sauté onions and garlic until translucent and fragrant (about 5 minutes).
Add peas and vegetable broth, bring to a boil.
Reduce heat and simmer for 20 minutes or until peas are tender.
Use blender to puree soup until smooth; season with salt, pepper, and mint.
Whisk cornstarch into 1/2 cup oat milk until smooth.
Heat remaining oat milk, coffee, and maple syrup in saucepan until warm.
Slowly add cornstarch mixture while whisking until pudding thickens (about 5 minutes).
Remove from heat, stir in vanilla, and cool slightly.
Serve soup hot, followed by chilled coffee pudding.