Place pancetta in a large skillet and cook over medium-high heat, turning occasionally, until evenly browned, about 5 minutes. Drain on a paper towel.
Fill a large saucepan with 2 to 3 inches of water and bring to a boil. Reduce the heat to medium-low and keep the water at a gentle simmer. Crack egg into a small bowl then gently slip egg into the simmering water, holding the bowl just above the surface of water. Cook until egg white is firm and the yolk thickens, 2 1/2 to 3 minutes. Remove the egg from the water with a slotted spoon and dab on a paper towel to remove excess water.
Place prosciutto on the toast. Spread a generous layer of avocado on top; season with salt and pepper. Add pancetta; top with the poached egg.