I am not sure if Plots.jl can do that. You could try using PyPlot.jl directly
using PyPlot
pie([15,15,30,60], explode=[0,0.3,0,0], labels=["A","B","C","D"], autopct="%1.1f%%", shadow=true, startangle=90)
Since PyPlots is based on the Python library Matplotlib, you can check the pie chart examples at https://matplotlib.org/3.1.1/gallery/index.html (translation from python to julia required, usually straightforward)