To blanch the peas, bring a large pot of well-salted water to a boil and set up a large bowl of well-salted ice water. Toss the peas into the boiling water, let the water return to a boil and cook for 2 more minutes. Drain the peas and immediately plunge them into the ice water. When the peas are cold, drain them and lay on paper towels to dry. Cut in half lengthwise and reserve.
Coat a medium saute pan with olive oil and add the garlic and red pepper; bring the pan to medium heat and cook for 2 to 3 minutes. Remove the garlic and ditch it - it has fulfilled its garlic destiny! Add the prosciutto to the pan and cook for 3 to 4 minutes or until crispy, then add the vinegar. Turn off the heat.
In a large bowl, combine the arugula, snap peas and onion along with the prosciutto and any juices from the pan; toss well. Add the pecorino and mint and taste it. Season with salt if needed and serve.