Preheat the oven to 400°F (200°C). Line a baking sheet with parchment paper or lightly oil it with a little of the olive oil.
Split the English muffins in half with your hands or a fork to preserve the nooks and crannies. Arrange the 8 halves cut side up on the prepared baking sheet.
In a small bowl, combine the softened butter and minced garlic until evenly mixed. Spread a thin layer of the garlic butter over the cut side of each muffin half.
Brush or drizzle the remaining olive oil lightly over the edges of the muffins to encourage crisping.
Place the baking sheet in the oven and toast the buttered muffin halves until lightly golden around the edges, 6–8 minutes, so they start to crisp but are not fully hard.
While the muffins toast, in a small bowl stir together the pizza sauce, dried oregano, dried basil, kosher salt, and ground black pepper until well combined.
Remove the toasted muffin halves from the oven and leave the oven at 400°F (200°C). Spoon about 1 to 1.5 tablespoons of the seasoned pizza sauce onto each muffin half, spreading it almost to the edges.
Divide the shredded mozzarella evenly over the sauced muffin halves, using about 3 tablespoons per piece and mounding it slightly in the center.
Top each muffin pizza with a few pepperoni slices, dividing them evenly. Sprinkle the grated Parmesan over the tops of all the pizzas.
Return the baking sheet to the oven and bake until the cheese is fully melted, bubbling, and just starting to turn golden in spots, 8–10 minutes. The muffins should be crisp on the bottom and edges.
For extra browning, place the baking sheet under the broiler on high for 1–2 minutes, watching closely, until the cheese is lightly blistered and golden in places.
Remove the English muffin pizzas from the oven and let them cool on the baking sheet for 3–5 minutes to firm up slightly.
Transfer the pizzas to a serving platter. Sprinkle with dried red pepper flakes to taste and scatter torn fresh basil leaves over the top. Serve warm.