How to Make It
Cook pasta according to package directions, omitting salt and fat; drain.
Place 1/2 cup milk in a bowl; whisk in flour and miso until smooth. In a saucepan, bring stock and remaining 1 cup milk to a boil over high. Whisk in flour mixture, reduce heat to medium, and simmer until slightly thickened, 4 to 5 minutes. Add pepper.
Heat oil in a skillet over high. Add tomatoes, and cook, stirring occasionally, until slightly blistered and beginning to pop, 2 to 3 minutes. Add thyme and garlic; cook 1 minute. Add spinach; cook, stirring constantly, until wilted, 2 to 3 minutes. Remove from heat. Add cooked pasta, sauce, and half of cheese to skillet; toss to combine. Serve in shallow bowls, and top evenly with remaining cheese.