Add pasta to pot of salted boiling water. Cook according to package directions. Reserve 1/2 cup of pasta cooking water. Set aside.
Heat 2 Tbsp. olive oil in a large skillet on medium heat until hot. Add asparagus, leek, and garlic. Season with salt and pepper. Cook, stirring occasionally, 2 to 3 minutes, or until vegetables are soft and fragrant.
Add lemon zest, pea shoots, 1/4 cup of the reserved pasta cooking water, the remaining 2 Tbsp of olive oil, and as much of the red pepper flakes as you’d like. Cook, stirring frequently, until the liquid thickens.
Remove from heat and stir in feta cheese.
Plate the pasta and top with freshly torn mint leaves.