Add potatoes to a large pot and fill with boiling water until potatoes are just covered. Bring to a boil over high heat, until potatoes are fork tender but not falling apart. Drain and set aside to cool.

Combine rinsed split peas and water in a medium sized pot, bring to a boil then reduce heat and gently simmer peas until cooked, about 20-25 minutes. Drain and rinse with cool water and set aside.

While potatoes and peas are cooking, whisk together olive oil, garlic, lemon juice, mustard, sugar, salt, and pepper in a large bowl. Julienne radishes and finely chop the fresh herbs.

When the potatoes and peas are cooled, add them along with the radishes to the dressing in the large bowl and toss to coat. Sprinkle with the herbs and gently combine. Garnish with more fresh herbs, if desired.