Step 1

Cook pasta in a large pot of boiling salted water, stirring occasionally, until al dente. Drain, reserving 1 cup pasta cooking liquid.

Step 2

Meanwhile, melt 1 tablespoon butter with 1 tablespoon olive oil in a large skillet over medium heat. Add shallots and stir until just soft, 3-4 minutes. Add garlic and 1 chile and cook, stirring often, until fragrant, about 1 minute.

Step 3

Add 1/2 tablespoon lemon juice and 3 tablespoons pasta cooking liquid to shallot mixture; add a pinch of pepper. Stir until liquid is almost evaporated, about 1 minute.

Step 4

Transfer pasta to skillet and add 1/2 cup reserved pasta cooking liquid. Increase heat to medium-high. Cook, tossing pasta or stirring with tongs, until liquid is almost evaporated and pasta becomes glossy, about 2 minutes. Add the remaining 3 tablespoons butter, 1 tablespoon oil, 1 tablespoon lemon juice, 1 teaspoon lemon zest, crab, half of mint, and more chile rounds, if desired.

Step 5

Stir pasta until butter melts and pasta is well coated, adding more pasta cooking liquid if dry. Divide between bowls; top with remaining 1 teaspoon lemon zest and mint. Sprinkle with more lemon juice if desired.