Preheat the oven to 350°F (175°C). Line a rimmed baking sheet with foil for easier cleanup or place a wire rack inside the sheet for extra crispness.
Rinse the drumsticks under cold water, then pat thoroughly dry with paper towels. Season both sides with sea salt and freshly ground black pepper.
In a mixing bowl, whisk together 1/2 cup Dijon mustard, 1/2 cup mayonnaise (or vegenaise), and the 4 pressed garlic cloves until smooth.
Pour the 2 cups of seasoned breadcrumbs into a shallow bowl wide enough to coat a drumstick. Set up an assembly line with the mustard mixture and breadcrumbs side by side.
Coat each seasoned drumstick evenly with the mustard mixture (use a brush or your hands), then roll the drumstick in the breadcrumbs to fully coat. Double-roll if needed to get a good crust.
Arrange the breaded drumsticks on the prepared baking sheet, leaving space between them so they do not touch. If using a wire rack, place drumsticks on the rack over the sheet.
Bake at 350°F for 50–60 minutes, until the chicken is cooked through and the juices run clear (internal temperature 165°F/74°C). For extra crispness, broil on high for about 3 minutes, watching closely to avoid burning.