If your budget isn't an issue. Try a "mass gainer". Meets your needs for quick, small serving. Preferably a mass gainer from a reputable company. Or make your own, cheaper and no fillers.
A mass gainer I make from time to time as a post workout shake.
2 scoops ON 100% Gold Whey
1 scoop dextrose
12 oz microfiltered milk
600 calories, 67 grams of protein
Hope this helps.