Bring a medium pot of water to boil. This will be used to cook the rice noodles.

Meanwhile, heat 3 cups water in a separate medium saucepan. When water is just shy of simmering, turn off heat and add tea bags. Cover and set aside for 4 minutes to infuse. Squeeze and then discard tea bags.

Put miso in a small bowl. Add a few spoonfuls of hot tea; then mash miso, gradually adding more tea as necessary to form a slurry. Pour slurry into tea in saucepan. Stir to combine. Bring broth to a gentle simmer. Add shrimp and bell pepper. Bring to a simmer once again; then cover and gently poach over low heat for 2 minutes. Remove from heat, keeping pan covered.

Cook noodles in boiling water according to package directions. Drain. Divide spinach among four shallow serving bowls. Top with noodles. Divide broth mixture among bowls. Garnish with green onions and serve at once.