Defrost spinach 10 minutes on defrost setting in microwave then drain well by wringing out in dish towel. Defrost artichokes as well, 6 minutes on defrost in microwave then wring out and finely chop.
Heat a sauce pot with butter over medium to medium-high heat. Add garlic to melted butter and stir 1 to 2 minutes, then sprinkle in flour and combine 1 minute more. Whisk in stock and milk and season with salt, pepper and nutmeg. Thicken 2 minutes then remove from heat and melt in Gorgonzola. Stir in spinach and artichokes and half the shredded cheese then transfer to a small casserole and top with remaining cheese. Brown and bubble in the oven for 10 to 12 minutes. Serve with bread sticks, celery hearts and pita crisps for dipping.